Re: SR-25 EMC or POF?
The KAC will be the most expensive. I'm still not convinced their civilian side customer service and support is all that great.
The Larue is very, VERY good. All gunmakers should have that kind of service.
The LMT will be very good and has the greatest accuracy potential due to how the monolithic receiver clamps around the barrel extension with a long and solid lock-up -- very much like a sleeved benchrest bolt action. Karl Lewis is also a manufacturing genius.
The KAC, Larue, and LMT uppers are interchangeable between lowers -- you can have multiple lengths and configurations for different missions/sports.
The POF has extra moving parts (the piston system) and a higher rail-over-bore height.
You will probably be pleased with accuracy out of any of them -- it will really boil down to a dollar and cost/benefit decision.
Don't discount an Armalite AR-10T Carbine with an LMT stock. For cost, accuracy, and portability it's still a good choice.