M40 is much easier to use, that is why it is the most used gun in CoD4 and public server. If you are like me, and play alot of consolemod, and EU tournaments, you'll find many Scopes using M40 and R7 unlike public servers where M40 reigns supreme. At the consolemod/MLG level of play scopes can use either gun effortlessly. The advantage to M40 is if you miss your first shot, not that you should be, when you scope back in, the cross hairs will be pretty much in the same position. On the other hand, the R7 does not do this, due to recoil. But i prefer R7 tbh, not too fussed either way.