Id say go with a Pistol Caliber Carbine (PCC), especially for indoor use. With a PCC ull be less likely to run into range restrictions, ammo will be cheaper and you and your neighbors in the bays next to you will be far less annoyed by the concussion and sound of the gun firing then that of a .223. The PCC will still be fun, in fact I find most PCCs have more felt recoil and muzzle jump then the semi auto .223's ...
AS for deciding which PCC , that is always a hard one.
Definitely take a look at:
The CX4 : a good blend of everything people look for in a PCC. IF you can get past its looks!
The Ruger 9mm Carbine : a less "tactically shaped" blend of everything people look for in a PCC
The FX9 : fairly new to the Canadian market, still hard to find in stock I believe.... Basically a tactically improved version of a Just Right Carbine (JRC). HOWEVER, they seem to be slightly less accurate then the JRC, and still appear to be less reliable then the gen 2 JRC as well. But most seem VERY happy with there FX9s!
The Just Right Carbine (JRC) : It really lives up to its name. Super reliable, super accurate, very customizable and excellent service and shipping from the manufacturer. The quick detach buffer tube system is a MUST! totally eliminates the disassembly complaint. Some models come with it now, mine didnt so i had to buy mine from JRCs website. Other cons would be the relativity high price compared to competition and unless u buy the take down model, the gun is pretty much the size and weight of a AR 15. Which can be an advantage and disadvantage depending on the situation.