Do a search in OSO as some of this has been discussed previously.
IMHO, it depends: how much horsepower, weight of the boat, how do you drive it, etc.?
For transmissions use Huber, BAM or the "shiftable" zero drag crash boxes from SCS.
All of the speedmasters allow you to swing a larger diameter prop and that can be an asset for some boats. But the speedy props are expensive.