I don't think hours matter all that much. It's quality, not quantity that matters.

I have just over 8000 hours. I fly with guys who have >16,000 hours. Are they twice as good even if I have more turbojet PIC?

I know an Airbus A319 FO who has just over 1200TT of which 700 is international, overwater, class 2 nav time in the A319.

Is he better than a CFI with 2000 hours who's total time is in piston a/c?

First of all, you have to define "better".

Is he more knowledgable and more experienced?

I'd say so!

AL