trader_4 says...

The most important info is missing. You have the old
one, you have the new one. Are they the same or not?

The new one looks generally like the old one did, which I no
longer have. But as I said, the old one had broken apart,
and the O-rings were super-stretched and would no longer
stay in place. But I concluded it was probably the right
size, although I had no way to tell if there was a
difference in the pressure required to turn it on. But from
memory, the original one worked better when the faucet was
new in 1998 than the replacement does now. But you know,
there were no regulations on water flow back then, and I
think it's possible they've changed all their diverters to
comply with new rules. Just guessing about that.

It's hard to imagine that Delta or Moen part is going to
fit a PF better than a PF part.

I was thinking it might be a good enough fit, but allow a
greater water flow.