The previous posts are right in that A-levels are much more easier to do than IB, myself being a 2nd year IB student now. The workload is definitely a lot lower, but the IB offers you skills that you are able to talk about in your PS to universities and in general the IB is placed higher than A-levels because of its demands on candidates.
University requirements for the IB is still ridiculously high as mentioned before, but I'd say the IB prepares you for uni life, in that subjects like TOK is like first year Philosophy at uni, and doing the EE teaches you how to write a proper research paper with citations and all.
However since it is mocks revision period now, there are lots of complaints (from myself included) about how we'd love to take A-levels instead since the pressure will be so much lower and we don't have to take as many as 6 subjects.
Make your choice wisely. I can say though that these last 2 years of high school has been the best and worst years of my life. :-)