Yes, there is a difference, especially if you are painting with acrylics. The 70 percent stuff may have things in it that interfere with acylic systems.
The 90 percent stuff is usually on a completely different shelf from the "rubbing alcohol" (70 percent). You may have to ask a clerk. In some locations, the 90 percent has to be kept behind the counter.
You can also use denatured alcohol, Everclear (ethyl alcohol) or even vodka. The latter two are only if you are at or over local legal drinking age, of course. Denatured is available at most hardware and paint stores.
For swabbing between coats of acrylics, you can try a dilute solution of Woolite, rinsed with tap water, followed by a distilled or deionized water rinse.