depends if you want gunz and mutants, or swords and dragons :D
skyrim is HUGE.. i have already invested 50 hours, and am not even close to finishing the game.. lvl 29 out of possible 50, and i have about 20 open quests at the moment.. even the lead developer of skyrim has said "the game is just to big..." FNV is big, but not as big, so if you dont have the 100-200+ hrs for skyrim, maybe FNV is better option...