Car appreciation... the aesthetics, the engineering, etc

On one hand, I can't see where I would find the time to race it (two young kids and a busy job are limiting), plus I'd need to stump up for the licence, a tow car and a trailer.

No point having a race car which you don't race. Says the man with a race car he doesn't race. So you can trust me on this one.

If you're going to race it, and race it reasonably soon, keep the B. If you're not going to race it, or if it's a case of 'I'll race it when the kids have left home/I've retired/Hell freezes over' then do the swap.