I'll add my bit for a B4 too (even though I run a XXX-CR
).
More people run the B4 so setup advice and spares will be readily available trackside. Every model shop I know of stocks B4 parts too.
The other up to a B4 is that if you do decide you want something else, it can be taken "to the next level" by converting it to an X6.
Ultimately though, get your mitts on as many peoples cars as you can and give them a go and then buy what you feel is the best for you.
Ian