I did extensive research and settled on the Tactical Carbine version of the Classic Army M15A4 (basically a full stock m4) as my first gun. If an Armalite is what you're looking for then I think it's the best of all possible versions. You have the shortened M4 carbine barrel, which makes you less likely to smack your barrel off something when turning quickly, combined with the full stock which houses a large battery. Small batteries don't have near the run time of a large battery, not to mention that the reinforced slip ring (the ring that keeps the fore-grip on) is really strong. While this is mostly a good thing and a big step up over CA's previous M15 versions, it makes changing small batteries in the field very difficult if not impossible.
CA's M15A4 series in general is a big step up over their previous versions and as far as stock armalites go they're probably the best. All metal where the real steel version is, the plastic parts where the real steal version is plastic are made of high quality enhanced nylon fiber rather then abs for great texture and feel. Classic Army has a deal with Armalite so you get all the proper markings. Plus that deal also goes to show the quality of the manufacture, Armalite wouldn't put their name on a shoddy product.
Internally the gearbox is reinforced metal and all the gears are metal as well. It fires hotter stock then Tokyo Marui's as well, firing at 300-320 fps where your average TM only fires 280-300 fps.
All in all this is a great starter gun if you can afford it. Because it's all metal you don't have to worry nearly as much about breaking it and you won't get any of the wobble or creaking that is infamous in stock TM M4/M16's. Unfortunately affording it is the biggest problem, they're not cheap. For reference I got my CA M15A4 from the classifieds, upgraded with a bunch of Systema internals to fire 390fps, for $600 shipped which was a great price.
As you can probably tell, I'm a big fan of Classic Army. One thing to keep in mind about Classic Army is they now have two lines, a proline and a sportline. Originally they were easy to tell apart because the proline had the metal body and the sportline had a plastic body but recently CA has been releasing their sportlines with metal bodies. The price tag should still allow you to easily tell the difference. All the pros that I went over above were regarding the proline model. The sportline model has cheaper everything internally and externally.
I'm not a big guy either, only 5'7 and this weapon fits me fine. The stuff I've loaded on the front of it makes it front heavy and overall heavy, but that's a price I'm willing to pay. You can always go with the streamlined version in the first pic. I have an mp5k-pdw as a cqb/loaner and it's very light, and very maneuverable. Even with the stuff I've tacked on to it (no pic but see my sig) it's still light and easy to move. I feel your pain when trying to keep a rifle up at length, it's worse with that grenade launcher I have on mine. The no add-ons version was much easier to aim for long periods of time though. The mp5k-pdw even more so.
My Classic Army M15A4 Tactical Carbine without external addons:
My baby, CA M15A4 Tactical Carbine with m203 grenade launcher, red dot sight and taclight: