While the majority of your analysis is spot on, Gerrick, I think the real question should be highly dependent on the character you play.
Obviously someone played with Evil karma wouldn't make the same decisions (or at least for the same reasons, which is also roughly as important) as someone with Good karma. Someone trying to look out for the best interests of the Mojave (perhaps played as a Mojave native) would make some fairly different choices from someone played as more of an NCR native (which would also be reasonable considering that your character has apparently made quite a few runs in the New Reno area), which doesn't even necessitate working for the NCR, as Caesar was also an NCR native. And of course it all really fundamentally depends on just how you see Ulysses throughout the course of the DLCs; if you agree with him on some fundamental level, then Independence, or House at the most, is the most logical choice.
Caesar's Legion appears at least initially fundamentally unappealing, of course, largely because it's a brutal fascist misogynist state. But I think there's a few observations that can be made there in favor of it.
1: It's taken like 80 (I think the exact number is either 76 or 79, I don't remember) tribes all across the western US and forged them into an army. It stomps out their individual cultures, but, I mean, so does the NCR. There obviously isn't as much divergence across the NCR as there is with tribals, as we most obviously see with the Dead Horses/White Legs (I mean, these dudes speak a fundamentally different language supposedly, at least to each other, even though for simplicity they all speak English to us; nor would it make sense for Graham and Caesar to be translators and linguists for the Followers if everyone just spoke English), but the re-formation of a monoculture is pretty crucial to an overall idea of a nation. Obviously this monoculture has a lot of issues with it, but some of those issues can be resolved, as detailed later.
2: One of the major points Caesar articulates is that he has his Roman Legion, but he has no Rome. An army must be run on fundamentally different principles than a state, and for all that he lays claim to having a state, it's apparently one without a capital city. The conquest of New Vegas and reforming it into his New Rome will likely allow for the transformation of the culture underlying the Legion into one that is less army, and more state. That will likely tone down a great deal of the martial law aspects of his rule, simply because in order for his state to meaningfully survive in that capacity (as opposed to simply breaking down into a series of large raider bands), it will no longer make sense for the majority of the manpower to be dedicated towards conquest.
3: Playing a female courier (especially one with good karma, and ideally one who can fix Caesar's brain tumor) who is Caesar's strong right hand seems insane. But I think that that would lay the fundamental groundwork for greater equality of the sexes, because it forcibly proves that Caesar's conquest would have failed without the intervention of this woman. For a society whose basis is at least partially founded on the idea that women are fundamentally inferior, seeing this refuted would likely prove a major step forward to the ideals of equality, and if a good character, will likely pressure Caesar to tone down the worst of his excesses - a move that might not be so effective were Lanius, who is a conqueror through and through rather than a would-be statesman, to come to power.
4: Breaking the Legion at Hoover Dam (with or without Caesar and/or Lanius' death) simply says that the Legion will turn its eye eastward and re-martial its forces. There will be no changes in how things run (barring the death of both); you have 'saved' the people of this area for the time being, but the people of the east will likely continue to suffer under their rule, whereas there is the very real possibility of change per points 2 and 3 for them above. Should both die, the Legion breaks up into raider bands, who will be even worse for the east than if Caesar and/or Lanius lived. Utilitarianism, bruh.
5: Rome's cool, bruh.
That said, there's a lot to be said for the fact that most of the time, you will be operating in opposition to Caesar's forces. Like, a whole lot. That in and of itself builds the idea that you should just crush them, simply because it's hard to stop fighting dudes.
NCR has a lot of points in its favor, but a lot of points against too. Admittedly not as many as the Legion.
1: NCR wants to bring back the US. That's a dope dream. Except the part where the US is a different US from the one we know (Commonwealths? What?), and it's also the US that invaded Canada without provocation (dick move), and also ended the world in nuclear fire (pretty dick move). But it's also the easiest culture to sell people on, simply on the basis of 'it's what we used to do, and would be doing, if it wasn't for the whole 'nuclear apocalypse' thing'. And as articulated above, while it flies in the face of our globalist multicultural ways now to want to create a monoculture, because diversity breeds strength and all that, it only does that if there is already a nation behind it. In light of few things keeping people together, it's imperative that people at the very least share a common culture if the goal is to rebuild civil society, to prevent civil war.
2: Capitalism. Hate it or love it, NCR's got it. And, on the one hand, there's a lot to be said for it, since - Gun Runners! Crimson Caravan! Colonial efforts! The fact that people have the spare money to go be fucking tourists in Vegas! But then there's always the bad flipside to capitalism. Crimson Caravan having people assassinated and caravans attacked for cheap buyouts, or doing indesp against the Gun Runners. Colonials coming in being seen as the bad guys because they're displacing the locals. And Brahmin Barons exploiting the working class. But all of these mask the underlying evidence we see that capitalism evidently works in the NCR, because look at Boston! There's no Gun Runners to supply you with weapons, there's no Crimson Caravan to promote free and easy trade between communities, hell, there's no Mojave Express to provide courier services should you need them. NCR has built the underlying components of a state thanks to their capitalist institutions; without them, Boston (and the Capital Wasteland too for that matter but I dislike Fallout 3) only has some scattered, disparate communities with relatively little linking them together, even ones in incredibly close proximity like Goodneighbour and Diamond City. Chrissakes, they have a fucking army with standardized equipment. That's nuts.
3: NCR is clearly relatively reasonable. House or Caesar won't work with the Brotherhood. They're a threat that needs to be disposed of. But NCR, who's been at war with the fuckers, is willing to make a peace deal with them and allow them to coexist. Same deal with the Enclave! Or the Khans (who Caesar will fuck over and exploit, and House just doesn't care about), or the Kings, or any of the other groups! Sure, the NCR has problems with them, but the other two factions will roll over the vast majority of them; only NCR allows these groups to live and let live (admittedly with your intervention, but, I mean, every faction only wins with your intervention anyway because you're a magic person).
I'm losing more and more steam as I go, so I'm just going to speed through the rest.
House has a lot of things in his favor too, but briefly:
He's also a capitalist (a 'bad part' of NCR that I've nonetheless shown can be a good thing);
He's also an autocrat (a 'bad part' of the Legion that can also be a good thing);
He's also a believer in a monoculture (albeit one that allows for subcultures; he's forcibly made the various Vegas tribes 'more recognizably American', but in ways that allow them to highlight their differences) (a bad part of both, really, but one that's probably beneficial to society as a whole);
But he's also a 'bad businessman' who seems pretty happy to stomp out various groups (e.g. the Brotherhood, the Kings, and of course he gives 0 shits about Freeside).
He's really the middle ground between the Legion and NCR, while allowing for better opportunities for advancement for the Courier (you're his right hand man, which is as high as you can go with the possible exception of Caesar?), and having the distinct advantage of being the earliest guy you work for. As players of games, we've been trained in an almost Pavlovian style to instinctively trust the guy giving us quests, and boy howdy did he give us a quest, since he's the driver of the majority of the main plot - very much in the same way that the Legion is easily presented as the bad guy, House is presented as the good guy, just from a 'who's giving me a main quest thing to do' perspective.
Since it's Bethesda, though, you can just kill him and everyone else really and go be Independent.
Which is terrible for society in the long run, but I've got a lot of Hobbesian viewpoints, so I'm a firm believer in government as a civilizing influence over people's innate barbarity. And since you're just one dude (albeit one with a shitload of Securitrons), it could also be a pretty awful thing for the people of the Mojave, especially if you have evil karma.
Next time: I edit this so everything gets the same amount of love I gave Caesar!
And then I talk about Ulysses, and how fucking crucial he is to picking sides in New Vegas.
