Why is sea salt better than normal salt? Or is it?

This link from the Mayo Clinic should answer your question.

http://www.mayoclinic.com/health/sea-salt/AN01142

You tend to use less because it has bigger grain.

No it isn't better as it doesn't contain iodine and regular iodized salt is one of the few ways we can get it.

seasalt is very concentrated therefore wen cooking even a pinch is too salty.

compare to table salt people go crazy pouring salt in their cooking thinking it needs more "flavour"