I never tried the B4.1, but I can tell you that the B4 shocks (v1) is not very good. I can never get them to work the way they suppose to. I have tried tamiya buggy shocks and they are awesome. Comparing tamiya to B4 shocks, its night and day.
I have read good comments on B4.1 shocks (v2) so I suggest you to get the B4.1 instead since shocks are very important in offroad.