Threaded helps if you want to use a muzzle device, ie brake/silencer, and it helps if you decide to sell it. Magpul mags worked fine in those I've owned.
If the price for a threaded barrel is within $30-50 of the non-threaded, I'd go with the threads 100%. No real disadvantage to threaded muzzle and there's always (for me anyway) the chance for a muzzle widget.