I've been thinking about getting an .223 AR for a good while, but I'm torn between an pistol upper (9mm) and rifle upper.  I like the lack of gas tube and simplicity of the pistol upper plus the ability to use the same ammo for both shoulder fired weapon and side-arm, also, sten mags are very cheap. Not to mention the lower cost of practice ammo. That said, I assume the a .223 upper would be much more potent, especially at longer distances.  
Does anyone on this board prefer the pistol caliber AR's to the .223's?  
What are the pro's and con's of each?

Thanks for sharing any thoughts/opinions.

Search back a week or two ago you'll see we did a similar thread (quite long) about the advantages and disadvantages of each (handgun, shotgun, and 5.56 carbine).

My recomendation is for the 5.56x45mm upper (16" lightweight configuration).  If you're going to shoot 9mm - might as well make it a handgun for concealability.

Ammo compatability seems to be a logistics issue.  *Magazine* compatibility is a tactical issue, and may or may not be a benefit.

And I haven't seen a great difference in cost between pistol ammo and 5.56 rifle ammo.

My primary home defense weapon is a Colt 45.

The AR is for last resort, I figure it should only take a few rounds to help extract the Bayonet.

Bill Paradise

9mm rounds won't penetrate IIIa body armor, but 5.56/.223 will.  No, you may never meet a bad guy wearing body armor, but the cops in Cali never thought they would either.

Your rifle is your primary weapon, the side arm is your back up.

Buy a good handgun (my carry is an HK USP Compact in .45ACP) and get a decent AR for sport and protection. I also bought a HK USC which is a rifle designed to shoot .45 ACP.

I live in a small trailer so a hand gun is much better there.

I can put a hand gun or rifle in the trunk of my car but I think the hand gun wins out here also.

With a concealed carry permit the hand gun really wins here.

The rifle as primary seems only to apply in a LEO or Military setting in which you are openly carrying.

Just my .02

We are plainly on the road to replicating the thread Forest linked to.  I'm along for the ride.

As long as the ammo penetrates 12-18" in calibrated gelatin with ~100% retained weight,  the weapon is robust and reliable with that ammo, and the shooter is trained with it and humbly confident in his/her skills, then that is the best weapon.

I think the indespensibles are training and a white light.  It's so much easier to go back to sleep when you *didn't* shoot the cat.

Thanks for all the reply's although I think I wasn't clear when asking my question.  I'm thinking more from a mechanical standpoint.
Is a .223 AR more reliable(feeding,etc)/durable(standing up to long term wear and tear) than a similar quality 9mm AR.  It seems like a 9mm or similar pistol caliber would be less prone to malfunctions and more forgiving in the elements than a similar quality .223 AR because of the lack of gas tube/fewer moving parts.
Guess I didn't word that very well when I originally posted the topic.....sorry about that.

Does anyone have experience with both types to know if one seems to hold up better than another?

I'd like to spend time shooting and not tooling around with finicky equipment.

thanks again.

Well said! (except for the part about the retained weight - I much prefer my 5.56 rounds to be fragmenting [;)])

Hands down the 5.56 is the better choice IMHO for reliability.  Much more service life & product improvement $$ spent on it to make sure its reliable.  Feeding in the bottleneck 5.56 round where the round is starting just outside the chamber is going to be more reliable.

Durability would depend on which 9mm kit you're getting.  Some are better than others (with Colt being the top).  I'm sure some 9mm parts may hold up longer - but how much longer?  Is it a significant enough amount to overcome the higher cost of magazines?

Forest: good catch, I was thinking handgun ammo.
And good point on the reliability as well.  Too many of the kits I see look a little tossed together.  Ideally, I'd go for a Colt-style kit on a post-ban lower.

My major problem with the 9mm AR is it's a step down from the 5.56mm in the same size.  A move one of the hotter .40 or .45 rounds (like 10mm or 45 Super) might be closer to a parallel move.