For a secondary weapon I would suggest you not get a spring. You'll want something that can fire in semi-auto.
Never get an electric pistol, I owned a cheap one once, and it broke, but from what I understand, all AEPs are cheaply made and don't last long.
I would suggest any gas pistol, even a CO2 over those choices. Most airsofters don't like CO2 for good reason, I myself like them better than green gas, but I suggest getting a green gas pistol. Browse around and select a few then post them back here and I'm sure you'll get more responses.