Not sure where you are with budget beyond the rifle but remember to budget for optics and ammo.
I personally have little preference with AR brand other than stay away from Norinco and BCL/NEA.
I've owned many different brands of AR's over the years and they've all been reliable and accurate. I wouldn't waste my money on a piston AR again, I owned a couple PWS AR's and they were fantastic but honestly I didn't notice any advantage over a regular direct impingement rifle. They simply cost more and have proprietary parts making them harder to get parts for in the future if needed.
The most import item in an AR is it's barrel when it comes to accuracy, you can buy a cheaper rifle then swap in a premium barrel and have a rifle that shoots just as well as a $2000+ AR.
One thing that spending more money up front will get you is better coatings and surface treatment, I like nitrided barrels it's harder than chrome and should outlast a chrome lined barrel while being slightly more accurate as well.
11 inch barrel? My personal favorite length is 12 inches, it's short enough for CQB type shooting and still long enough to give enough velocity to be effective out to 300 yards.
Longer is NOT more accurate so don't go with a longer barrel for that reason. Longer barrels do give more velocity which translates into a flatter trajectory but the quality of the barrel (and quality of ammo) is what makes it accurate not it's length.
I used to own a 6.5 inch barrel and it would shoot about 2 moa at 100 yards with quality ammo and one of my 12 inch rifles would shoot one moa with quality ammo.
I would buy whatever AR you find that fits your budget and is decked out as close to your personal tastes as possible. AR's are fun to modify but if you're just going to buy the cheapest rifle then change everything on it you may as well just buy a receiver set and build one instead of paying for all the parts on the cheap one just to take them off and sell them or throw them in the parts bin.
There are lot of options, only you can decide which option is going to get you where you want to be for the price you want to spend.
Building from the ground up will not be cheaper but it will get you exactly what you want. I would suggest that you go to a range and try to shoot as many different AR's as you can, if you're really new to this you may not know what you really like until you handle and shoot a few different rifles.
))) so stoked 
