Hedge funds tend to be a lot more blue chip and technology-driven than IBs. IBs are usually filled with a lot of legacy crud -- some of it well-written, a lot of it.. not so much -- and a completely different culture as the earlier poster cynically talked about at length. I don't agree with everything he says and it sounds like he's in NYC and not London where things are generally of a higher calibre as Finance generally pays above and beyond what you can get in other industries.
Right on - London vs. US is very different. I envied my UK friends who left work at 4pm on Fridays to have a drink with their colleagues, when I'd regularly be working till 8 or 9pm.
I currently work in finance in London and have experienced very different! I was nervous, expecting to be working with MIT gods who would make me feel like an embarrassment of a human being. The reality is I am working with borderline retards from Utah who do no work whatsoever and when I explain in detail, they don't listen one bit. I'm the one left working 50-60hours to cover their lack of work.