30% difference in speed, so yeah it's significant. That'd mean .. ~8min for the C47 vs ~11 for the Junkers, for an adjacent field capture assuming 25mi distance. But you're still dead slow in the C47 and have to plan in advance what your path to map room or friendly GVs is going to be, so there's not much difference in that respect. And when you're caught there's no chance of escape unless it's a Val or something chasing you down.
In a situation like Grizz describes, which is the majority of the time in AH - correct me if I'm wrong, 160 or 230 mph is no different as far as survivability is concerned. The fast fighters catch you in seconds and the slow ones have little chance of missing their shot once they're caught up.
I think we'd have to have it in game to really see if one of the two is clearly better.