I've got both. Two PLR's and a Bushmaster Carbon 15.
Between an off the shelf AR pistol like the Bushmaster and the PLR, no contest, the PLR.
The PLR costs half what the AR pistol costs.
My PLR's are more accurate than most of my .223 rifles.
The action using a AK type piston and AR type bolt, IMO, is far better than the AR gas impingement system.
The PLR nine inch barrel gives 2,550+fps, the seven inch Bushmaster muzzle velocity is 2,300 fps.
The Bushmaster is not as accurate and hasn't been as reliable as the PLR's.
If the PLR breaks or wears out it will be repaired or rebuilt at no cost.
I don't know about the Bushmaster.
And I think the PLR is a good looking gun. I call my AR "The Paint-ball Gun".
I'm thinking about buying two more PLR's but not considering buying another AR.
But if you are thinking about swapping out uppers, like polik6887 said, a AR would be the way to go. With the PLR .223 is it and I haven't heard of anything else in the future.