Personally I hate highcaps.
-They rattle when you run around
-You have to wind them, sometimes excessively
-When empty, they're a pain to reload in the field
-They encourage poor trigger control, especially in new players
-Reloading non-highcaps under fire is A LOT of fun, and people who only use a highcap are really cheating themselves out of this.
Personally I use standard magazines (50r for my G36) and lowcaps (30r for my MP5). I have a couple of mid-caps but I only load them to 50 or so rounds anyway.
As for magnifacation, 4x is probably a little excessive. 1.5 or 2 would be fine for airsoft.
"Someone in a Prius tried to race me at a stop sign the other day. I couldn't believe it. I had him for the first 100 feet or so but I can only walk so fast."