Bottom line you will have, by far, the most choices in the category of
conventional trailer boats with i/os. If you do not want a real
inboard ski boat then I'd look in this category. If you are staying in
protected water I would also go with a bowrider.

If he's outgrowing the boat then a bowrider probably isn't what he's after.

What're the limiting factors of your current boat? What extras are you
looking for? That might help better determine what alternatives to
consider.

The usual issues apply, I/O and outboards can be trimmed up but I/O's have
maintenance issues if you're leaving them in the water. Inboards are the
best for maintenance if it's in the water all the time but don't have the
shallower drafts of I/O's. Jet drives have efficiency issues, especially as
you into larger boats.

But it raises the question of what is it you want out of the boat ABOVE the
waterline?