Instant Ocean- I would use this if you are trying to get extra nutrients out of your system because it is a low nutrient salt mix.
Reef Crystals- This is a good standard salt that is inexpensive and low in nutrients as well. It has higher levels of trace elements then the Instant Ocean and higher calcium levels.
I use SeaChem Aquavitro Salinity- I have been very satisfied with this salt mix. It is very concentrated and mixes up quickly. Also, It has higher levels of calcium so you don't see a big drop in your calcium levels when you do a water change. The mix is very precise as far as the levels of calcium 409-435, magnesium 1296-1376, and strontium 8.1-8.7. I also really like that is has a full analysis of the salt on the side of the bucket and the analysis is very accurate.
Besides those three salts my favorite salt is Tropic Marine Pro Reef

but its expensive :/