Free Net Pass isn't bad, I've never used the other two.
If you want a good free avs to use tho go with Free Age Card. $25/join and $20/recurring on free signups, and their ratios are as good as the others, I've used several. You can't beat recurring on free joins
I know everone recommends things so you'll use their referral code, and I'm gonna put mine, but I'll also link without it, it's your call as this is a real recommendation not just a shot to get some people under me
Sign up with me as a referral
Or just visit
http://www.freeagecard.com
Your call, but I'd of course appreciate the credit