Hmm, a SquareD QO220 breaker costs $15, while a QO220GFI breaker costs
$90. I have two induction motor loads, a jointer and a dust
collector. I wonder if the greater expense of GFCI protection would
be a good reason not to rewire these motors to 220V.

You use your jointer right after stepping out of the shower? Why do you
want a GFCI?
Bear in mind that to get 240v you have to contact both hots. That is highly
unlikely, and wouldn't trip a GFCI anyhow. Assuming your tools are grounded
properly, any kind of shock (except from directly touching one of the wires)
is unlikely, but would be exactly the same as a 120v shock anyhow.
(I shouldn't admit this, but in the interest of full disclosure... while
drywalling I forgot an outlet was hot and pulled on it, contacting the hot
with one hand and the neutral with the other. Fortunately it was just a big
surprise, but I might not have been so lucky with 240v! Stupid things like
that are possible. A GFCI would not have helped because there was no
current leakage.)

To answer your other question, the hots are interchangable; there is no
reason to distinquish between them. Accordingly, you have to mark the white
wire with black tape on both ends so no one mistakenly thinks it is a
neutral. You might want to think about using 4wire so your hots will be
black and red. You will have the white available as a neutral if you ever
need it. I didn't do that when I ran 240v to my shop and I regret it.

240v is no more difficult to wire than 120v, but you might want to read a
wiring book first, because you don't seem to understand what 240v is. It is
no more difficult when you know what it is; when you don't get it, I suppose
a dumb mistake could easily happen.