Had a lively exchange with Norman Stanley Fletcher (Easyjet) about this subject a few years ago.
FWIW, I'm one of three former Q400 capts to make the jump from LHS turbo prop to LHS A300-600. It was really no big deal and we all managed the course in minimum time.
IMHO, what counts is the quality of the operator and not type you fly. That said, not all employers are as broad-minded as ours and you will quite likely come up against the 'TP hours are worth nothing' mentality from time to time so it's a hard one to call.
Good luck whatever you choose.