I prefer Fallout 3's radio since it has more variety. There is jazz/blues, there is patriotic drums-and-trumpet music (although hilariously limited, albeit catchy playlist) and classical. Fallout 3's songs were usually faster paced, which added more feeling to the adventuring. Extra points for Ink Spots'
Maybe, which is a must-have for every Fallout game

An obvious flaw for both is limited playlist, but that is perfectly understandable because there is no need to spend too much money on song copyrights when you can put that money to better use.
Not that I feel any contempt for NV's radio... However I don't listen to it often, since especially Radio New Vegas suffers from audio unbalance. I don't want to raise volume for a song only to have Mr. New Vegas' voice explode into my ear afterwards. Plus, you can always kill Three Dog if he gets to your nerves.
EDIT: My FO3/NV song top five is 1) Civilization 2) Big Iron 3) Heartaches by the Number 4) Let's Go Sunning 5) Maybe