The 22 is a dedicated 22 rifle and just looks like an AR the 223 is a true AR
My first answer when asked what to buy is "what are your needs" are you looking for home defense, plinking, target, long range, just to say you have one?
depending on the answer would dictate my reply
If you want a long range setup I would first suggest another platform like a bolt action or a M1A if AR is still what you want I would suggest a bushmaster varmenter or other long barrel fixed stock type rifle
If you want to be impressive build it yourself or have it built to custom specs By the time you purchase rifle, rails, grips ect.... you will have replaced 75% of the parts and will have spent 75% more than needed
Target (200yrd to 75yrd) I would recommend a 20" gun with fixed stock from any of the standard manufactures in reality there is not more than 5% difference between most guns only real difference is the cute picture on the side.
home defense or plinking I'd recommend a 16" or SBR carbine The smith is an excelent choice but you can usually find a stag arms (the co that builds the smith) between 50 and 100 cheaper just for the logo on the side.
personally I have owned many AR's I have only purchased one factory built one Buy one of the ridiculously cheap receivers buy some parts here and there and snap it together I'm sure many here, including myself, would be more than happy to help with any problems