Looks have (almost) nothing to do with it.
The Turboprop moves a large mass of air at relatively exit pressure, low velocity. Great low-speed (takeoff) performance, and efficient cruise at moderate airspeed. Limited in max speed, however.
Turbofans use the case and shroud and fan stators to achieve higher pressure ratio, higher exit velocity, mostly benefiting high altitude cruise.
BTW: taking the turboprop to the logical extreme, turning the shaft to vertical with a very large low-speed prop, results in a VTOL machine such as a helo.
You pays yer money, you takes yer choice.
