Not enough information ...
To actually answer your question, you really haven't explained for what purpose or how you plan to use the weapon. This makes it hard to advise you either way.
If you are looking for urban SHTF protect your family, then the AR14 M4 4 or 6 position stock with 14.5 or 16 inch barrel with 1:7 twist, with the right dot sight will probably be a good choice Note: others may argue, but on a AR15 with with less than 20" inch barrel I would not recommend using M193 class ammo!
If you go AR15 with 20" barrel typical Service Rifle competition than the .223 is probably a great rifle.
If you are looking for more fire-power then one of the .308 rifles may be a good choice, however, I would caution against getting a AR in 308 that has a barrel less than 18" in length. As others have already mentioned, .308 ARs (Armlite AR-10, DMPS LR-308, RRA LAR-8, POF-USA P-308) are all different with different parts and are not interchangeable.
I'm going to mention something else for you to consider: If the urban defense weapon sounds interesting to you, I would like to suggest something else for your consideration, and that is either a different upper and mags or as complete rifle. TFL already knows IMHO what i think of short barreled AR-15, so will set that aside for the moment. However, if you want real stopping power, aren't worried about over penetration, think apartment complex, then I would suggest you look at a AR-15 in 6.8 SPC, this cartridge was designed to function well in a 14.5 to 16 inch barrel and has better terminal and barrier ballistics. The real cool thing, is other that bolt, barrel and magazine it uses standard AR15 parts.
A couple of comments to consider: 1) AR-15 platform is available is more than just .223 cartridge, AR-15 allows for interchanging upper and lower receivers, my brother has two AR-15 lowers, one with a A2 fixed stock, and one with M4 6-position collapsible stock, M4 16" 5.56mm upper receiver, M4 14.5 inch 6.8 SPC upper and NM A2 upper. With these five units he mixes and matches to suit his needs. He is talking about getting a A4 upper in .243 for deer hunting. 2) I would spend some time thinking about how you will actual use the rifle and do some research both here and at the Ar-15.com web site to refine your choice/decision. 3) I agree with those who say you should start with AR-15 first.
My last comment is I take exception about Bushmaster rifles not being good quality that has never been my experience, however I never bought an assembled AR-15 in my life, and even uppers I bought were tore down and reassembled by me. I am a engineer, machinist and gunsmith, so the only person who does work on my weapons, is me, my self I, hey it is crowed in here. But with the AR-15 platform, the cost of the right tools is not cheap or for everyone, some will say all you need is wrench, but don't believe them, gauges, holding fixtures, disassembly blocks, pin punches, hammers, etc all cost if you don't possess them. And head spacing is not a simple job, and requires the right tools. Thus if you are looking for great quality already assembled weapons, than choosing the right manufacturer or supplier is important, if you are like me, then the quality of the parts is more important than the name, and I know how to verify the quality of parts
YMMV
