I can't give you a definitive answer, but I can relate to you what we were told when we bought ours.
ISOFIX makes it, like you said, idiot proof to to install. So, assuming everything else was the same (seat design), an ISOFIX seat is likely to be 'better'. The problem is that because ISOFIX has this additional feature, it can artificially inflate the rating of a particular seat.
So, if you had two seats, with a similar rating (but of different design), it's possible that the ISOFIX version had been given a higher rating due to the fixing rather than the safety of the seat. And that in the event of an impact, it may be worse for a baby than a correctly fitted non-ISOFIX seat. ie it 'might' not be as padded for the head.
Of course these were all theoretical arguments or points and at the end of the day you have to make a choice that you're comfortable with.
In the end, we looked at both, but took the advice given and ended up with a very well designed, non-ISOFIX seat. When correctly installed, there was really no movement.
Does all that make sense? |