Artificial tears differ in viscosity and whether they have preservatives.
It depends how dry you are and how often you surgeon wants you to put your drops in. If you have severe dryness, one of the more viscous brands would be appropriate, such as Refresh Plus, Genteal, or Celluvisc. If not, then any of the other brands would be fine. Ask you Pharmacist to help you figure out which are the more viscous [thicker] brands. The down side to using the thicker drop is that it will make you vision a little more blurry, as expected.
As far as preservatives go, if you are using the drops more than 5 or 6 times per day, then you may become irritated by the preservatives used in the bottles. If that's the case, then switch to the single vial, preservative free drops. You can use these as frequently as you need them [once an hour if you need]. You have to use them that day, obviously because of lack of preservative. The downside is that the cap on this single vials are somewhat flimsy and you can't put it in your pocket or your purse when you open it once, because the fluid will leak out. Once open, leave it on the counter.