Different products, different denaturants.  They might look at you
funny if you start sniffing the containers, but the label is often a
clue.  I buy the cheap stuff with 4% or less methanol.  Benzene is a
known carcinogen, so I'm not sure whether they use it to denature 200
proof (100%) alcohol these days.  VWR lists a bunch of denaturing
additions for ethanol, but I don't know what's used by Ron Hock, for
example.

There's no real point in paying the premium for potable 190 proof
alcohol, but it should be free of poisonous additions.

Other bits:

The highest potable alcohol you can buy is 190 proof or 95% alcohol +
5% water.  It's really hard to get 200 proof undenatured alcohol
because it has such a strong affinity for water.

The other good stuff for solvent use is isopropyl alcohol -- you need
the 99% pure stuff, not the 70% (or less) rubbing alcohol stock.  It
evaporates slower than ethanol, I think.

Ken Meltsner