"Ski boat" means different things to different people.
Enough power to deep water start the heaviest slalom skier, with eight adults in the boat?
Ski around the lake riding straight behind the boat?
Enough space, storage and a head so you can be on the water all day with ladies on board and accommodate small bladders?
You like to jump the wake so bigger is better?
You boat on a huge windy lake fighting with other boats throwing large waves, so a smooth riding deepest V-hull is priority?
Any boat is a compromise, so you just need to prioritize. I ski on a small lake, early a.m. with one or two friends. We don't need to haul people, the water is flat or we don't ski. I share a 12 yr old Malibu LXi. (Open bow, 340hp 5.7L) with an aftermarket exhaust that makes it one of the quietest boats on the lake so as not to annoy neighbors. And we ski 34 mph short line, sometimes in the slalom course. I'm spoiled, a bit of a snob even as I dislike a lot of other ski boats if there is too much spray or a funky wake dip at 35' off.
At the same time I pretty much love all things skiing and have skied behind about any kind of boat out there. I'm just an advocate of skiing with whatever you've got to work with.
That said, if you get to choose, I'd avoid I/Os of about any kind, in preference for an outboard powered rig. About 600 lbs less weight in the back of the boat means better hole shot, and smaller wakes once planing. Lower deadride (less V) in the hull helps too, so bass-boat based fish and skis ski pretty darn well. Otherwise I would choose a 18' bow rider with 150 outboard over same hull with a v6 or v8 I/O. Similar hole shot and always a better wake.
Assuming you like to slalom back and forth through the smallest wake possible, that gets my vote.
If you are skiing fast enough (my opinion, on the high side of 30 mph) so a direct drive's wake flattens out. If the weird interior layout works for you, and you can put up with rough ride on a windy day, a direct drive in SOME years and models can be a beautiful thing.