For the most part I'd say you are pretty close. Stepped hulls are more efficient and will run a little faster due to lower propslip percentages and cat hulls are even more efficient.
There is also the diffence in what rpm the engine is designed to run. It is best to prop them at the upper end of the recommended WOT range. Going from a 7.4 to 500efi, that would be a 500-600rpm difference.