wow...thought this was pretty straight forward... 120. It's like 2mp versus 15. It's easier to blow up a picture with more resolution.
Hmm, I wonder if the question was just posted to get a thread on the film forum in analogy to the full fame or cropped sensor thread in some other part of TPF
I prefer 35mm More shots per roll, smaller cameras (generally). as long as you dont want to blow up to a massive size 35mm is great!
I guess it depends on how big you class big as... If you already have the kit, then I would stick with using the 120, as you'll be able to blow the shots up a lot bigger than 20x24. But then again, it depends what you're going to be photographing. 35mm cameras are generally more convienient for fast action (sports, wildlife etc), or for 'candid' photography where discretion is required.
You can make large prints from either. Good prints from 35mm REALLY good prints from 120. My vote is 120.