I don't know EnviroFile, but i hate $harecash. It's not available in alot of countries, and it's just always buggy.
Sharecash is obviously better.
ADF.LY you just wait for a sec or two.
Sharecash is better than envirofile because they are lot of payment proofs for that , whereas envirofile just joined the revolution
$harecash is good, people make like almost 7k in 1 1/2 month
There's also another one, Dengee.net
None, be cool don't make good people fill out surveys.
I personally use ShareCash, haven't even heard of the first one you mentioned. ShareCash is a good side way to make a little spending change. There are many techniques you can use to get more people to download your file.
All crap IMHO. Some may be lucky enough to get paid. Most dont. Not worth the effort. Seriously not worth it.