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LMT if you plan on mounting anything out on the rail.

WIZZO

I would get a LMT upper with a KAS or LaRue 7' rail installed that is my next projet. I love to have a LMT MRP 16' upper, but they cost to dang much. You could get a LMT 16' upper and get a LaRue 10' or 12' istalled and come out cheaper in my opion.

I have other preferences, but of your options I'd go for the MRP.

Some one correct me if I'm wrong, but I believe the MRP has 13 or so less parts than a standard AR configuration. It's also lighter. I have no personal experience, but from what I've read it's also a very efficient tack driver. On a general guess, I'd also think the one piece upper and forend mating would make it more rigid than a standard upper. (Although it's doubtful that will ever be proven or necessary)

However, the non standard gas system components could be hard to come by if any problematic issues were to arise. You also have to carry around a tool to change and/or retorque the barrel.

Quoted: You also have to carry around a tool to change and/or retorque the barrel.

This is true.  I love my MRP, but I wouldn't take it to war.  That's just not what it's best at.

You can get a Noveske, ADCO or MSTN upper is you want stainless, ortherwise get an M4, add a LaRue gas block and a long LaRue rail.  At least 9.0.  They are very stable.

Quoted: You also have to carry around a tool to change and/or retorque the barrel.

You will need to carry around a Barrel wrench, a Torque wrench, and a table mounted vise if you want to change the barrel on a conventional M4 style upper

I have not heard of any issues with MRP barrels coming loose when they have been properly installed/torqued.

The MRP is heavier than a conventional M4 upper with a LaRue or similar set-up, unless it is a Colt M4 HB/SOCOM upper, then they are about the same.

I have 2,000+ rounds through my MRP without being cleaned, with NO function problems at all, and NO loosening of the barrel. It is pretty heavy though. Mine is set up with a 16" CL barrel, an Aimpont M3 in a LaRue mount, Troy front BUIS, and a LaRue rear BUIS, A Dieter VG and a LaRue BattleLight and it is heavier than anyones similarly set-up M4 upper that I have handled. But I wouldnt trade it for anything, and I do trust my life to it.

I've been intrigued by the MRP since it came out.  Toyed with the idea of buying one.  Decided against it as I can build a nice FF upper, equip it with good optics, and still come out even or cheaper.  I'm sure it is a nice piece of gear as MRP owners are happy with them.

You need to ask yourself what requirements the MRP fills for you that a regualr upper will not.  The answer will be simple then... either it does something nothing else will do or its just money and weight wasted.  I have zero use for the MRP.

I like the MRP a lot...but proprietary barrels and the cost keep shying me away.

Quoted: Quoted: You also have to carry around a tool to change and/or retorque the barrel. This is true.  I love my MRP, but I wouldn't take it to war.  That's just not what it's best at. You can get a Noveske, ADCO or MSTN upper is you want stainless, ortherwise get an M4, add a LaRue gas block and a long LaRue rail.  At least 9.0.  They are very stable.

It's not for war?!?  What the hell is it for then?    You need tools to set the headspace on an M2, I guess it's not for war either.