I was thinking about the 9 but if 45 is a better choice then I will look at it. My reason is that the only two barrels I have that are suppressor ready are 9 and 22.

If all I ever wanted to do was 9mm, then I'd never get a 45 can. it adds to every parameter that matters more sound, weight and dimensions.
On the other hand it reserves options for the future, but the cost of these things really isn't huge. But while I know its 'workable' just get a .22 can for rimfire. They are cheap and way better than using a centerfire can even if you can clean it.