I've been using race fins made by Larry Allison for over two years now, and I really don't need to try anything else. They do everything I need a race fin to do; track well, reduce drag and shed weeds.
My first Allison fin was the Eric Terrien Bat Wing. I was amazed at how well it made the board track and how many more strokes per side it allowed me. It made the stock fin look like total junk.
Then, last year I discovered the Gladiator fin, made by Larry with design ideas from fellow SUP racer Casey Gotcher out of Austin Texas. He runs a great SUP site called SUP Gladiator. http://www.supgladiator.com/
Casey and Larry just came out with the new Hybrid Gladiator fin that is a slightly smaller version of the original. I used it for the first time in a race last week and won the race on my 14' Bark Dominator.
There are some very different designs attributes between the different models, and Larry can explain the advantages to each... he talks like a hydrodynamic/physics engineering doctorate student, but all you really need to know is that any of these fins are probably better than what you use now.
If you live in Washington, you can buy any of these fins at Perfect Wave Surf Shop in Kirkland, or order the Gladiators directly from Casey.
Above: the Hybrid Gladiator. A great fin for a 12'6" or 14' board in low wind/current that will do buoy turns easier than the standard Gladiator or Bat Wing. Keep in mind though, that this fin will work very well in windy conditions too, but has slightly smaller surface area than the other fins. The Hybrid will also work well in downwind situations, and be loose enough to turn from bump to bump.
Above: This shows the Bat Wing laying on top of the original Gladiator. The Bat Wing works great on 12'6 and 14' boards, but I really like it on my 19' Unlimited.
Above: This shows the Hybrid on top of the original.
Above Left: Original (Elite) Gladiator. Use it on long distance paddles when you aren't having to do a lot of tight turns. It will keep you going arrow straight.
Above Right: Hybrid Gladiator. The points on the trailing edge of all these fins gives water a definitive point to release. Otherwise water has to "look" for a release point, causing resistance and drag.
The race fin quiver... The red/white/blue fin is the Thresher that excels downwind and on flat race courses with lots of turns.