Ooh, hard to choose.
I like crowntails because they tend to move more freely, and I also like the ones with slightly shorter tails and fins so they can act like fish. The longer-finned ones can be gorgeous, but I like my fish to move. Not a fan of the Dumbo-ear ones.
The fish in my icon is Bismuth, one of the prettiest bettas I’d seen in a long time. Never could photograph him right, but he looked just like his namesake, this nice shimmery metallic color overlaid with greens and blues and a hint of light purple depending on how the light hit him. I tend to prefer blues and greens and shimmering colors.
I also really like wild-type bettas like B. albimarginata.