Here is my take on retracts...

They are a major PIA. If they didn't look so cool, no one would bother with them. But they DO look cool and they really clean up your airframe. So they are somewhat of a necessary evil.

This being the case, keep them as simple as possible. To me, this means: If you don't have a nose gear, go with mechanical retracts.

You can get a retract servo for about $30 and a set of Mechanicals for under $20. Air retracts will set you back about $120

PLUS - With an air system, the retracts are in the wing and the rest of the stuff is in the fuse. This means that every time you put the wing on and off you have to connect and disconnect the plumbing (And make sure it doesn't get trapped between the wing and fuse). With mechanicals, you only have one extra servo to plug in.