I've chartered both power and sail cats several times. I have plenty of sailing and powerboat experience and I don't own a charter vessel so I'll stay out of the argument about charter companies renting to inexperienced sailor.

If you plan to navigate under power most (or all) of the trip, there's little difference in the platforms. The horsepower difference doesn't really matter. The sail cats will typically go 7-8 knots under power, which is plenty fast enough. You can move a little faster in a power cat (12-15 knots MAX, in my experience) but you will pay dearly in fuel costs. Trust me. I know. Sail cats practically sip fuel. Advantage: Sail cats.

I don't find the rigging to be a big issue on deck. You have to walk around the standing rigging but it doesn't really get in the way. Still, power cats have no rigging so navigating the decks is easier and more familiar to a power boater. Advantage: Power cats.

The big advantage of power cats over (most) sail cats is the extra space gained on the fly bridge. That's actually the thing that draws me to the larger power cats most of all. It's a very nice thing when you have 6-8 people on board looking for their own space to get away. Advantage: Power cats, for sure.

The nice thing about sail cats is it's easy to find good deals with 2nd and 3rd tier charter companies. Foot-for-foot, sail cats are cheaper to charter. Advantage: Sail cats.

For me, it's almost a wash. It depends on who I'm taking on a particular trip, what boats are available, and what kind of deal I can get.

Oh yea, another power boat option to consider is Virgin Trader. They have a small fleet of motoryachts. I've never used them but I hear the boats are well-kept and service is very good.