In theory, it is better to have a clean prop over the wings, but that only lasts so long... I wonder how many pilots realize the danger they face with tailplane ice. It often gathers at an accelerated rate compared to the wings, and in many planes (like TBM 700s) the tail is not visible. Trot along on autopilot long enough with your head up your backside and all of a sudden (from the pilot's perspective) the autopilot goes off and the plane goes all over the sky, uncommanded. Sound like fun?
As far as why the heated prop with no other protection, it is the same reason as having TKS on a Cirrus with no known-ice certification (besides Cirrus not wanting to pay for the process of certifying it....I assume they're still not known-ice at this point)...it'll help get you out of the clag and into the clear. Better just to stay out, but crap happens. When it does, it's a tool to keep the occupants of the aircraft in one piece.
Last edited by Nathan_Meese; 10/09/08 12:29 PM. Reason: I R Smahrt