Hi buddy the only way to definatly get a premium grade L27 of any type is to buy large 12" + unfortunately, due to the fact they change so much during growth from being small,a lot of the way they look can also be manipulated by tank conditions aswell, especially the colouration, what I find people tend to look for is unbroken bright yellow stripes and a nice tail mainly, that's just in my experience of coarse, and I'm not an expert, if you looking for the best one that's very subjective unfortunately as it's down to personal opinion because what I like may be very different to what you like, personally my favourite is the L27 armbrusteri xingu, think there classed as a L027A they have a more slender body and head, they also get a bit red on there fins when they get a bit bigger, I find them to be a bit more unique as I find other types of L27 just look to much like L190 but slightly different colours, but back to what I said before the best one is what you personally like the best, I like the armbrusteri xingu due to its unique features on the other hand you may not, really its down to personal opinion, hope this helps
