I'll mostly be using whichever phone I choose for internet, texting, phone, and music. Maybe some other things as well but those are the main points. I'm thinking iPhone now because all of my music is on iTunes anyway, so the transfer of music will be quite easy. Plus, I'm also thinking about size (no pun intended). Since iPhone is a bit smaller it'll be easier to fit into my pocket rather than the bigger Galaxy S3.
Damn, I didn't know choosing a phone would be this hard.