Just that.  The variant section goes on about the CZ.  Here I see a good post on the JRC.  No where do I see favorable reliability for AR based 9mm's.
NFA goodness is just 4 sets of fingerprints away if I go that route.

Seems the CZ Carbine would be sweet if Geiselle would ever make a trigger for it.

Poll needs None of the above. I've owned 3 AR 9mm 2 Colt pattern 1  Glock a Scorpion pistol and a Sub2K but never a JRC. I've come to the conclusion that pistol calibers should stay in traditional pistols. PCC's are a waste of money.

I don't want one myself.  anything an PCC can do, I can do with my 22 carbine.  BUT.  3 gun nation has created the PCC class and I am interested.

Have several friends using the Sig MPX with good results. Taran Tactical makes extensions for the MPX as well.

I have a couple of JRCs, 2 AR15 type 9mm rifles, and have only handled the CZ. Did not like the feel of the CZ personally.

I like the way the JRC rifles feel while shooting as they stay pretty flat with the lighter weight bolt. Not finicky on ammo at all. Biggest problem is the controls. Bolt is hard to rack and mag release on the left side.

For 3 gun, I think the AR style is the way to go just because of the controls. The lowers from PSA or Joe Bob's take Glock mags and there is plenty of tuning you can do with buffers and springs to make the rifle feel the way you want it to.

The MPX is really nice as well, but that definitely gets into more money.

For some reason I could not vote, but I would say 9mm AR.  And I own a scorpion SBR.  The biggest reason I would say that is the scorpion trigger is just not precise enough for 3 gun competitions.  I have installed the lighter trigger spring from HB industries which made a big improvement but compared to an AR trigger it still leaves much to be desired.

I think that if an aftermarket trigger is ever available for the scorpion that would make it a contender.  Despite the fact that you would not have as many parts to customize with as you would with an AR, I think that the scorpion charging handle location and handling is better than the AR but there is also something to be said about familiarity, and since almost everyone else shoots AR style for rifle, the familiarity would be good.