Which is a better base for a stage rally car ? Any opinions gratefully received

I would say the STi unit would be a better unit for such, but dont forget, its only as good as the management programming at the end of the day. Its not the engine that gives out, its the programming that is not 100% which causes the failure.

the sti engine should have tastier internals such as steel crank and forged pistons.

Cheers
Za