IMO......
Erythinus sp. Peru is shy and not very active. Erythinus erythrinus is the more active fish. Gold wolves Hoplioerythrinus are a good choice as they don't get to large and naturally shoal so play well with others.
On the aimara - curupira point.
Honestly it depends on what you are after and the price difference.
I have two of each.
The curupira are a great fish and to a point with a big enough tank ok with other non wolf fish that are too big to eat. They are active although I have found in a smaller tank 4' they tend to sit there. In my 8' he always swims in the open water.
Aimara tend to be more interactive as mine are always wanting to eat. I do however expect as they mature they will slow down. My two are currently 10" and 17". There is a very slim chance that you will be able keep them with others. As a single fish this is propably the one to go with.
It's difficult and given the choice I'm not sure which i would choose. If you were looking at an aimara I guess you would have a fairly large tank and it may be better to have a curupira and a couple of pbase or something like that.
I haven't helped at all really have I.
http://www.youtube.com/watch?v=saifaP2HmG8