I own both. Get the M1 Carbine. It's a blast to shoot, a historic piece, parts are common for making it a little more vintage. It does make a decent Whitetail rifle when within 75yds using SP/HP. It makes a decent home defense weapon as well, when loaded with the same SP/HP. It hits harder than a 9mm/.45acp pistol.
The Kel-Tec is a cool gun. The ammo is cheaper... it again makes a good plinker. Wouldn't hunt with it(even where legal). I think .223/5.56 is not a prefered home defense load, even with SP/HP... too much chance of over-penetration unless you hand load it sub-sonic.
Get the M1.
For those who fight for it, life has a flavor the protected will never know.