In my opinion, it depends on your reason for the water changes.
For example, if you're wanting to lower nitrate levels, or correct water quality problems ... doing larger water changes several times a month would seem more effective as mentioned above. You'll only lower the nitrate level by the percent of water exchanged with new.
Providing the new saltwater is nitrate free, and little additional nitrate is being produced in the tank.
If you do a 5% water change - you'd expect to only get a 5% drop in nitrate ( at best ).
But if you're levels are pretty good - I think doing a small daily water change would be ideal.
As long as the new saltwater is mixed/stored well, I don't see a problem.
Then again ... some will argue if the levels are pretty good to begin with .... why do the water changes ???
But as stated above, by bringing in a small amount of "new" saltwater each day, you may find that you need not dose the tank as often, that the tankwater chemistry becomes more stable and the obvious "less-shock" to the system.
I think you'd have to do this over a long period of time ( months ) before you would notice any benefits.
Kind of depends on the tank size, number and type of fish, existing water quality, evaporated top off schedule and whether you're running carbon, skimming or using a refugium too.
Lots of factors can affect "each" of our need to do water changes.
