IMHO it's not worth the extra expense of finding the other varieties (gold, long finned, etc). If they happen to have them in the store, get the ones that you like best. I personally think the original is as nice as any of the others.
The longer finned strains are very pretty and show their fins very nicely. I have both the wild type and golds in my tank. They are both very pretty. I just need to pick up some java moss and I'll probably have a few hundred more of them in a few weeks. My females have gotten very swollen as of late and my males are dancing all over the place.
As for your tank I would go with the golds if you can find them. You have a darker substrate and they will really pop out.