Actually, I think that if a professor says to you, "if you pay for it and show up, I'll teach
you the course," I think that's a pretty damned
special(!) opportunity. You just might get a few months' time
one-on-one (or, nearly so ...) with "a person who seriously
knows."
"You
will work your a*s off!"
But you should have known that from the beginning, because you've actually bought a segment of
a professional's time ... and such opportunities, properly and seriously handled, can be
priceless. Not only will you learn the material, but you will
also have made "a professional contact," and earned "a professional reference," from someone whose credentials are stellar: "s/he is a
college professor."
Obviously, you should properly explore both opportunities. You have
two(!) colleges at your disposal. But you have, at one of those two colleges, an
individual who is willing to invest his/her time in "even
just one student." The two institutions are, of course, "not in competition with one another," but both of them presently have something to offer you. Drop by the offices of both places (during published hours, of course ...), and ask more questions. Let [both of ...] them help you arrive at what is the best decision for you.
(P.S.: My [experienced ...] first-reaction to your comment was ...
"gee, students like you are rare! ... I like to work with 'students like you.'")