From a purely practical standpoint, depending on what other firearms you own you can have magazine / ammunition commonality. (Ruger/Ruger, KelTec/Glock/Beretta/SIG/S&W, Marlin & any .357 revolver, etc..)
They tend to have very mild recoil. My wife doesn't like shooting most of my centerfire rifles, but my Marlin .357 doesn't bother her at all. But then neither does my AR-15.
For a fun gun, the Kel Tec & Hi Point 9mm carbines are inexpensive and fun to shoot. I own one of the newer 995's and it's just fun. I used to have a Kel Tec SUB 2000 but ended up selling it, but that was just personal taste.
On the other hand, for the cost of one of the nicer/cooler carbines (Beretta, Uzi, etc...) you can buy a really nice 5.56 carbine that packs considerably more oomph, doesn't recoil any more, isn't any larger, isn't any heavier, has less expensive 20 & 30rd magazines and tons of after market accessories.
I have to admit, if I ran across a really good deal on something like a Ruger PC9, I'd probably buy it, but I'm not going to go looking for it. We can trade pros and cons all day long, but it really comes down to what you want.