Maybe it's the tool I bought, but whenever I use my new oscillating
tool I'm just not impressed with it.

Cutting wood takes too long. Cutting metal (cuting nails) takes much
too long versus a Dremel. And it's LOUD.

I bought a Menards-brand Li-Ion cordless model. Is there THAT much of
a difference versus the others? I can't find a review that implies
cheap oscillating tools are necessarily worse than, say, Rockwells.

I know that cheap power tools aren't as good as expensive power tools.
But when I buy Harbor Freight I get about 80% of the effectiveness and
ease-of-use.