I ran a B4.1 for a year before switching to the C4.1 as I've always stuck with Associated stuff. It was the best move I've ever made.
It's almost worth running the B4.1 for a bit to fully appritiate how much better and easier the C4 .1 is to drive on high grip tracks. Other than the better handling, the conversion makes the back end of the car so much more simple, making it much easier to work on.
