That my friend is an age old discussion with no clear answer.
Oceanic and Reef Crystals are a solid lower cost brand you may want to try out. You can get reef crystals in the box for quite a bit cheaper if I am remembering right. I also hear good things about the base Tropic Marin salt.
It all is personal preference, and lots of people will jump salt mixes from bucket to bucket depending on whats on sale, with no ill effects. There are actually some really beautiful tanks maintained in this fashion.
Do some searches on the site concerning "Salt Mixes" there is enough reading and user experiences there to last you a lifetime.