For something like a fin nipping barb or tetra, all you are doing is paying extra money for what will be a short finned fish in a week.I aggree. The stores frag tank is a disaster. I have no freshwater puffers at my store thankfully. Are longfin varieties impared? Elaborate
Long fins also make it a target for any other fin nippers in the tank.
The fins cause a lot of drag in water and make it harder to swim. Compare a veiltail betta to a wild type, the wild type is going to be much faster and more agile than a fish that has to lug a huge fin around.