* No one has made mention that there is a massive difference in the type of teaching between these institutions. UCLA wold be regular assessment, multiple choice. LSE got just four 3hr exams at the end of the year. More scope to fall off the rails at LSE if you are the kind of student that gets distracted - and can't write essays (on your own, under time pressure).
* All these institutions are similar in that they tend to have big classes, and can be impersonal. They all have good reputations. Reputation is in part fostered by size... the bigger, the more chance of finding good scholars. UCLA is biggest.
* There was reference made to culture either. LSE will be the most international. UCLA least (the "foreigners" at UCLA are more likely to adhere to a US cultural and financial ethos, so less diverse ideas). UCLA is more likely to have a fraternity-type culture, with insufferable rich, ignorant and drunk US males. Montreal is marked by the anglo-French confluence right on its doorstep.
* Costs: I think a more realistic assessment in £88,000 for UCLA, £50,000 for LSE..., and far less again for McGill. Quite a big difference to your own estimates. Obviously you are not paying, else you would have had more precise numbers (your are more likely to find rich ilk at UCLA). LSE is at an annual cost of around £10k fees, £4k at Passfield hall (incl food) for a 40 week contract and £2.3k other expenses. Caviar and vodka extra.
* Montreal is certainly the best city to live in my books. McGill is at the top of a hill, with a lot of greenery behind it. But there is no ski slope on campus. LSE will be best from the point of being in a capital city (the only one of the three) with a great speaker list, every day.
* Don't worry about the government / economics divide. I am told you don't learn all that much as an undergradaute. Employers are more concerend about the institution. Afterwards, they look at the specialisation. Govvernment and Politics is a great mix if you want to do international political economy. That means themes like development, curencies, globalisation, etc.
* A major major advantage of UCLA is that it is easier to change programs. Hey you may find your life's passion is in medieval Spain or stellar theology after all. IN LSE, you ae boxed in to your course. McGill is in between, but more like UCLA.
* By going to the US, you would be implicity supporting an economy and society that wages perpetual war on small nations, and keeps them in poverty by unfair trade restrictions, and this is supported by a majortity of voters. Not for me. In London now, there is a real chance of dethroning Blair, as so many voters now see how they are manipulated and lied to. But despite US responsibility (or the lack of it), you are far more at risk from terrorism in London. This is no mean risk. Just a few weeks ago, a Russian was found at the Hungarian border with a few kilos of caesium and plutonium. It is just a question of time. It might not be a "nuclear" bomb, but a "dirty" one. London has to be the prime target, especially if gung-ho Blair remains in power. In Montreal, you are far safer from every point of view.
* The year is 40 weeks in McGill, 31 weeks in LSE. In LSE, there is more the expectation that you will teach yourself, or that your friends will teach you.
* There was another thread on McGill and Toronto with more info on McGill.