I have them and they are the best! My 2005 Tige 24V has lockers that are just a little short for them, so they scrunch a little (about 4 inches). They are well worth the extra dough, IMO. They are strong and durable.
Depends on your boat. I have a '00 X-Star and I could have gone with the 750's on each side of my engine. I would measure your compartments first and see if the V-Drive set fits perfect for you or would leave a lot of extra space. I would rather have the 750's not filled all the way that the V-Drive set with room to spare.
Other than that I love them, very durable great connection for the Tusnami pump. I recommend them to anyone.