Let me see if I can clarify this for you.
For 2008, you had 10 different models of Supra.
1. Launch 20
2. Launch 20SSV
3. Launch 21 V
4. Launch 22SSV
5. Launch 24SSV
6. Gravity Games 24SSV
7. Sunsport 20V
8. Sunsport 22V
9. Sunsport 24V
10. World Edition (ALL NEW for 2008 ) on Launch 20, Launch 20SSV, Launch 21V, Launch 22SSV and 24SSV models.
The V indicates V-drive to distinguish it from the Launch direct drive which they introduced back in 1999. They had both models until 2008 which was the last year for Supra to make a DD boat. See number 1 above.
The SS indicates Sports Seating. It is a model designation found on the Launch series only. You will not find a boat called the Sunsport SSV as it had the walk-through bow as MJHKnox indicated earlier in his post although the Sunsport did have rear facing seating configurations. There are no SV/ SK designations either.
The Launch was more pro rider where as the Sunsport catered to the weekend warrior or general watersports enthusiasts crowd.
From the beginning, the SS models had the Rad-A-Cage tower, 3 bag ballast system, adjustable wake plate and a swivel head pylon. Supra actually had rear-facing stadium seating on 2003 models which are standard nowadays hence the Sports Seating designation. The 2008 model allowed up to 6 passengers to directly face the rider.
For 2008, you also got the Gravity III ballast bag system which was a 300% improvement over earlier bag systems along with the Perfect Pass and the SmartPlate which allowed you to add up to 8 riders with their preferred settings.
The Supra Ride System optimized straight-line tracking, speed control and time to plane while automatically adjusting at all times to rider preference for wake shape and hole shot. You could also upgrade to the new 6 liter 409 HP if you had the extra cash.
Hope this helps you out.