I think out of all of them 6 has the best fins.
Number 1 is pretty nice but I don't like the ventral fins at all and I think his pattern could be crisper than it is.
Number 2 is very nice. My only issue is again the crispness of the BF pattern and the fact that his caudal is a little uneven. Not a big deal at all.
Number 3 has nice fins but his body looks short to me and his color is a little too dilute for my taste, but that's a matter of preference.
Number 4 has great fins also but I'd like to see a different picture of him. I dunno.. something just looks off. Maybe it's because he looks stressed out.
Number 5 's fin are "meh" to me. I like his caudal but his dorsal, anal, and ventrals need work IMO.
Number 6 has nice color and pattern and a really nice dorsal.
I would go with either 6, 2, or 1.