Emo tends to be more about trying to 'out-different' other emos. They started with dressing in mainly black and being dark, then one bright kid thought "If I wear pink and listen to dance music, i'll be more different", then everyone else caught on. Things like skinny jeans, plimsole shoes, tight band tshirts (Or the new 'in' thing appears to be 'retro' or 'geek-chic', so Mario tshirts), tight hoodies, usually with the hood pulled up.
The main difference I find, is that a Goth mindset is "I'm different and i'm fine with that. You know it, I know it, deal with it", whereas an Emo mindset is "I'm different, I need to make you know this, so hopefully listing off lots of obscure bands will help you realise this".