The JG Bar 10s are always raved about. Not sure about the other ones
My friend has the UTG L96 and it's pretty good. It's not really accurate enough to use it over an AEG. The power is good though.
Honestly, airsoft snipers are fun, but unless you upgrade them a lot, they are useless. (Heck, most AEGs with TB barrels could still get the same range as a sniper)