The main reason NOT to start with a SR is that you have NOT established your gaming style. A sniper is a very defined style of play and also requires a certain amount of discipline and developed specialized skills. Most noobs think it would be cool to play sniper boy.....but get bored when they are actually required to sit and wait for maybe one or 2 shots. Most noobs want to be where the action is....and also tend to expire a disproportionate of rounds relative to targets achieved (not very sniper like).
Start with an M4 (which you can bling to death)....figure out how you like to play(maybe if you like tons of rounds down range....you might like the role of SAW gunner) and go from there.....
Playing sniper boy can be very rewarding.....and sometimes very boring......and you definitely shoot way less!
Semper Primus: Always First