For general purposes not involving long range shooting, the M4 Carbine models are just more compact and lightweight overall -- depending on your accesories of course. But if you keep everything to a minimum, a carbine will serve most uses and will be as reliable if set up correctly.
The other compromise as others have said is a mid-length with a 16 or 18-inch barrel. My 300Blackout middy with 12-inch rail was a good setup without the longer rifle profile and heavier weight.
I'd love to build an AR15 rifle length in the future..