How easy is it to convert a 9mm ar to something else? i didn't realize it was something simple to do.I went with the SBR'd AR 9mm. Not the coolest by far, but it easily converts to something else if I ever get tired of it (not permanently, of course - I would still keep the means to readily convert it back).
Also, parts are readily available and it's easy to understand how it works. It's a familiar system of operation to most of the folks on here.
Colt mags - other than the Uzi, you probably won't find cheaper mags than these.
Just some pluses...
If I had to choose between the scorpion and the mpx, I would probably go with the scorpion because of costs. The 9 carbine is kind of range toy anyway and the mpx is stupid expensive for what it is.
I don't necessarily think it would just be a range toy. It would be pretty good for home defense and something I could easily put in a bag or in the car. I'm thinking it could be a pretty practical little gun.
Everyone says not to go with the mpx because of cost but a lot of people have over $1k in their 9mm ars and the mp5 clones are even more expensive.
I think I'll update the OP to say "I've got it narrowed down to the sig MPX, CZ Scorpion, mp5, 9mm ar, or UZI".