Andy, they are genetically different, it's not just appearance. There have been 3 different strains of albinism discovered in leos so far, which you listed above -- Tremper, Rainwater, and Bell. If these animals are bred together, no albinos will be produced as the different strains are not compatible -- you would just produce babies that were het for both strains. To the best of my knowledge, nobody has yet produced an animal that displays 2 of the different strains, although many double hets have been produced.
Hope this helps a bit

Jen