L96A1 or M24, that depends on with what you feel more comfortable. Basically, for any skilled player constantly aiming for the head of another player those rifles are a must.
Usually, that's what Snipers do: They look for cover behind friendly lines and support their team by taking out key enemies (by that I mean gunners in Vodniks, HMMVs, Tanks, etc.) and other threats such as enemy snipers. With a reliable rifle you'll be their nightmare (believe me, I've defended the Hotel in Mashtuur against 2 transport vehicles and 6 infantrists just with my L96, one Claymore and my Knife, completely visible for the enemy squad(s) right ontop of the little nearby house roof, lining up one shot after the other).
I've also made the experience that people tend to react nervous but not horrified when you shoot them with semi-auto guns and that they will look for some shelter, a medic and soon for you, dear rapid-fire sniper. As soon as they see you, you're done, at least I doubt you'll be superior to a PKM or a G36 type on an urban map, also the L85A1, F2000, G3 can easily take you out very quickly. So be prepared to... run!
Hitting someone with one of the larger caliber rifles though, will imprint some confusing effect on your target, except the target is a medic and close to some shelter, which can possibly still be blown up by a well-placed frag grenade...
What I want to say: M24 and L96 are my first choice on any map, urban or not, because you practically hit the head if you properly aim for it and have the feeling for your ping. You can risk an enemy spotting you, shooting at you and you will still get him (Don't you fellow snipers also love to take out proning spec-ops that have already hit you once and now think their G36C owns each and everyone? ).
See you on the Battlefield (Maybe through my Scope, muahahahaha),
Stormscythe