I am currently doing A levels and my twin sister is doing IB at the school I went to for my IGCSEs, so a lot of my friends are also doing IB.
My sister gets more work than me. There is no question about it. The amount of coursework she has to do for the IB is immense. But is it harder? I'm not so sure.
I'd say there's definitely more work, but this doesn't mean its harder. (Though maths HL is DEFINITELY harder than A level maths.)
I also think my sister will be more prepared for uni than me. She's learnt how to reference properly, come up with her own scientific experiments and carry them out, write a super long paper... (speaking of which, the EPQ is definitely not equivalent to the EE). You only need to read the IB learner's profile (BS as students might say it is) to realise that the IB has a completely different approach to education than A levels.
As for the "different" standards in offers from unis, I don't know much about this, but what I do know is that Cambridge collects a lot of data and compares IB / A level grades to succes in the uni course, and makes their offers accordingly. This seems pretty fair to me.