I think in normal 7.5 m2 conditions (14-17 knots maybe) the Futura would be faster than the Kombat, and also more forgiving.
If you want fast, I'd suggest looking at the Isonic 122. Should be good on fairly flat water to 18 knots or more and it's quick and fairly easy to sail.
If you are in the USA I know where there's a near perfect Isonic 122 (my board from last year on consignement) for a very good price.
On the skill level involved, I'd say the Futura is the easiest 122, then the Kombat, then the Isonic, but the Isonic planes earlier than the Futura, and significantly earlier than the Kombat so you get a bit more time on the water with the Isonic and get going significantly faster, earlier in the wind spectrum.
The Kombat is very nice, for more bump and jump type sailing. It's quick but not in the same class as the Futura or Isonic, and with the lower volume tail, it will not plane as early as either of the others.
Another board you might consider is the 2007 S-Type 126. It's quick, jibes pretty good, and may be as fast (in some conditions) as the Isonic.
Hope this helps.