(I originally posted this at 12:37, but it never appeared. So here it is
again, with a new paragraph that starts with "Another advantage."

I'm trying choose between the 4" Sioux Chief with the three red rubber
seals for $22.99

http://www.acehardware.com/search/in.../19541496&sr=1

and the Sioux Chief 3" x 4" just above it and to the right for $2.99,
that fits into the drain pipe very snugly, but has no seal. Thus I would
rely on the wax ring to seal against odors.

I was originally going to go with the one with the red seals, relying on
friction to secure it to the drain pipe and to securely anchor the
toilet, hoping to avoid drilling into the concrete floor to attach it.
But Sioux still recommends attaching it to the floor. So if I have to
drill in either case, why not go with the cheaper one?

Another advantage of the cheaper one would be easier to remove if future
repairs are needed, since it's not glued to the drain pipe. I don't know
how hard it would be to pull out the one with the three seals.

FWIW, the flange will rest on top of the finished floor.

Thanks,

R1