It's entirely up to you, but the one thing i'd say is that the B4 is very common so spares are easily obtained at any race meeting even if there's no shops.....
Other thing to think about is that there are so many B4's about that Set-ups are easy to come by and the car is very easy to get right.
I think they're getting there with the X-6 but it's still quite new and may be a bit "specialist" if you know what i mean, but again they're going well now and getting some good results.
I would imagine it'd be easier to buy a good 2nd hand B4 and at least try it to see how you find it, then it's just a case of converting it to the X-6 - at least that way if you don't like it you've still got the B4 bits to put back on?
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