I wouldn't necessarily say IB students are always asked for higher grades though - for example, some unis like Warwick want STEP from A levels if studying maths, whilst they don't need this from the IB student - a 7 in HL maths is enough. I'm not saying a 7 in maths is definitely easier than passing STEP, but I reckon it potentially is easier to study for... it all depends on what type of person you are. I remember going to their open day, though, and asking why it was the case that they don't need STEP, and I remember him saying something along the lines of "because in the past, all the IB students we've gotten have been very, very good."
Overall I reckon I maybe maybe might have done better with A levels - ha, I haven't even taken my IB exams yet but they're in 2 weeks and I'm just estimating - because they're modular and if you're the type that's good at memorizing, and studies hard for each exam you do, etc etc then you maybe could achieve the top A* level grades easier than getting a IB 7 - but I personally think the IB gives a more rounded education.. and I really did like CAS now I look back on it, as much as I whinged and whined at the time. So if i went back in time I don't know which I'd choose again. In 10 years' time hopefully I'll be saying IB.
Aside from all this though, that comment about grades getting remarked 4 marks higher scares me a bit..