I have Honda 20's with the 28 inch shaft on a 44 foot around 6 tonne boat. They're plenty of power, cavitation isn't a problem, they work very well.
However I recently installed a pair of Tohatsu 20's to a similar boat. They are available with a 25 inch shaft - a 5 inch factory made extension is fitted by the retailer - and because of their more compact bracket, their actual propeller
works out to be pretty much the same as the Honda's.
There are some photo's of the installation
here: Recovering From TC Oswald.
All the specs, for power, weight, gear
ratios and props are very similar to the Honda's, but the Tohatsu are a fair bit cheaper. IMO easier to service
too, as oil
filters etc are more accessible.
I'm very happy with my Hondas, but if I was repowering I'd almost certainly go with the Tohatsu 20's now.