I'm definitely a bigger fan of the gymnogynes types since their morphology is so different depending on the collection location (pictures are from my past 2 collecting trips)! Also I'd like to give G. tiraparae (picture #1) another shot sometime in the future but in at least a 125g.
I've kept G. gymnogenys (Quilero), G. labiatus (Rio Olimar), G. meridionalis, G. tiraparae (Rio Yi) and G. balzanii. Of those, the gymnogenys were the most interesting and colorful (pics). Currently I have a young male tiraparae and he's just starting to perk up in color. In my experience the gymnogenys and tiraparae are more aggressive than the others, but nothing over the top. Best to keep a male with several females.