I'm putting in a new cold water heater along with the wire to run it. I
will be using 10 gauge solid with a ground wire, and stapling it to the
joists in the crawl space under the house.

The old wires were single wires run through a flexible conduit. The big
boxes I called said that romex 10/2 w/ground would be fine to run in the
crawlspace, stapled to the joists.

One store recommended style UF, the other said just any old romex would do.

What say you: single conductors run inside a conduit, regular romex, or
romex UF?

Jon