I'd prefer the first way 'cuz it's better to develop all of your fingers. Thats what I think. I maybe play for almost two years, but I always try to do pulls & hammers with all of my fingers. Now I have a problem with hammering with my pinky, when my middle finger is already fretted. Like holding a barre chord and fretting some note withe middle finger and I have to do a few notes with my ring and pinky, which often tend to be hammers with the pinky and thats pretty hard for me to do it clean and hit it strong enough, although I play an acoustic.