Guess it depends on who you're selling it to. If it's someone here, or mud, etc. I'd be inclined to leaving it, as they'd likely understand what it's about, and what they need to transmit, etc. But if it's a trade-in, the I'd yank it for sure. Random CL sale would fall somewhere in the middle I guess..
if you can yank it and leave the wiring behind, that's probably best. Then odd chance the guy buying the truck is already a ham, and you can then add back the radio to sweeten the deal.