I've got both an M4A1 (ICS) and an MP5 (TM).
Both have their uses, in the right environment. Both are interchangeable within those environments.
The M4A1 is my primary outdoors field weapon. I've got it set up so that i can have an aimpoint on it for CQB'ish/short range engagements (with handle removed), and a 4x32 Telescopic scope on either the removable handle via a dovetail mount, or mounted directly on the rail, with the handle removed. I can throw a tactical flashlight (surefire clone) on it for night events, or a Harris bipod, if i feel like camping in the weeds with the telescopic scope. In short, it's my do it all, swiss army knife of rifles for airsoft.
The MP5 comes into play, when i'm tired of toting the M4A1 around. I'm currently playing airsoft for an unusual reason. Physiotherapy, post double hip replacement. After a while the M4A1 can get on the heavy/unwieldy side if i am getting tired... and the MP5 can be quickly switched to for a package that is much more compact, and lighter by a good margin - allowing me to stay in play for a little while longer. It's got pretty close to the same range as the M4A1.. i'm not really at a disadvantage with it, in terms of engagement effectiveness at all. I've also equipped it with an aimpoint sight, and I have also got a flashlight for it (integrated into the forestock of the Navy version MP5A4) so i'm not at a disadvantage at night-time with it either.
The advantage of having two - beyond the advantage that each may possess over the other in any given situation, is that you have a back-up rifle close at hand, should one go down for whatever reason. Both are equally as comfortable in my hands.
So in short, i ain't got an answer for you as to which is the better rifle to pick.. I like 'em both, pretty much equally.
Last edited by HackD; March 15th, 2012 at 15:53..