Subject: What to do.

Not quite.

If you have an all seater and an all bench, set at the same price, more fans would turn up for the all seater than the all bench.

Yes but if you have a mix, you will get more on the benches than at the seats.

Yes. But if there are no benches, they will join the other seat sitters. So therefore All seats > All benches.
(edited)

hence why i said a mix is best

I'd have one stand set for seats, minimise the rot. :D