Back on topic; I think if you looked at like for like, in terms of kg/ seat mile terms the turboprop will generally beat the jet hands down. That would be the case for say, Vickers Vanguard vs Caravelle to Q400 vs A320.
Thing is, the fuel costs in the Vanguard days was such a neglible component of overall costs: legacy overheads and all that. Today it's somewhat different, that's not to say there aren't heavy engineering and technical costs with some of the turboprops, and yes, if you want to get there on the same day without stopping for refuel en route (additional costs), you fly on a jet.
But in a pure calorific value of fuel for work done basis; the turboprop wins.