[Harbinger of Darkness]

A good bet might be to fill out your profile a bit more to let us know where you are. From there you could always get out to a game or a retailer's location (if they are open to the idea) to hold the gun and see how you like it before you invest in it.

To ansewere your questions about the vertical grip and rail system. In my experience I find a vertical grip to be pretty useless unless you have an M16 lenght gun. I'm 5'7"ish and I use an M4 - I find myself holding the mag well more often than the vertical grip. As for the rail system it can really come in handy. It will allow you to add; flashlights, lasers, knives, other guns, the kitchen sink, monitor lizards, well you get the point... :P
If you like to accesorize your gun then a rail sytem can defiantle come in handy.