I have been around experiments with both painting and dacaling on a variety of aircraft. My opinion is paint it!
Depending on the aircraft, and where the "object" is to be placed can make the differance where the logo is to placed. This can't be learned except by trial and error.
Some aircraft are exceptionaly clean in some areas, meaning that the decal won't last.
The Merlin III B, forget putting a decal on fusalage forward of the cockpit and on the nacelles. Gone in a 100 hours, nothing left but the glue.
The Lear 25 & 35, forget the fusalage from nose to engine inlets, nacells OK. Tail OK. Under the cockpit side windows, 25 hours maybe.
Metro III decals are OK anywhere on the airframe except nacelles, heat and oil oozing.
Cessna 441, okay anywhere, go figure, it's a fast, fly high airplane.
Any piston twin, okay except on nacelles, to much oil oozing.