I have the 7.62x39 model, and I love it. I wasn't sure if I would like it, I've seen plenty of negative reviews (based on poor reliability and poor factory support), but the gun has completely exceeded my expectations.
The pistol versions are very light, the carbines have a heavier barrel profile.
My 7.62x39 is more accurate than I was expecting. I wanted a modern 7.62x39 that I could use to shoot cheap steel ammo and the gun has really impressed me.
Magazine avability and reliability are two problems you shouldn't have to worry about with the 5.56 model.
The 5.56 model didn't interest me as I already have AR15s, however, now that I've had experience with the bren 2... if I were looking for a lightweight carbine in 5.56, I'd probably pick one over another AR at this point (but I wouldn't be without an AR15 of some kind). It's just a really well thought out weapon. It's light, has ambi controls, has a really nice folding folding stock, the factory trigger is quite nice, as are the flip up sights.
My only complaints would be too heavy of a barrel on the carbine model, to short of a handguard on the pistol model.
Personally, I would buy the 14" pistol model, then buy the 922r kit and pin and weld the barrel to 16" inches. Then potentially buy a longer handguard if the factory HG is too short for you.
I think the 14" model with the factory stock (and flip up sights) should weight about 6.25 lbs, which is where I like my carbines to be.