I'd recommend getting both if you can swing it. if you can only get one, get the #50 or a UBR 10, which has a fine side and a coarse side.
probably my favorite rasp is my UBR 10. the fine side of that rasp is phenomenal, and probably what I use the most of all my rasps. the coarse side is good for hogging off stock quickly, but I seldom use it, favoring draw knife or bandsaw if I've got that much to remove.
I think you can still get UBR 10 at
www.bowyersedge.com tell Dean young Jamie sent you.