I think you're going to get very mixed replies for this question. As someone who started out with a spring airsoft sniper rifle I think I could provide some insight. Unless you go to a dedicated milsim game you're not going to be of too much use. I entered into airsoft with 6+ years of paintball and the few games I have played were all pretty evenly paced with scenario paintball games. To add to this, many fields have special restrictions for snipers which can make it a bit of a hassle if it's your only weapon.
To be honest, any decent spring rifle platform is going to cost you just about the same as a decent AEG. Stock for stock, they will both have similar effective range. If you're that dead set on a sniper role, I would buy an AEG and mod it to a DMR. The effective range for both a spring platform and an AEG platform is really going to depend on how much you're willing to spend. You can make an AEG outrange a spring rifle just as easily as you can do the reverse. I guarantee you will enjoy having the AEG more.