Yeah the focal length of the scope makes a lot of difference to the image scale, for example I use a scope of ~350mm focal length to squeeze in Carina and Andromeda but there are lots of smaller objects that would be framed better in an 8" f/4 newt with ~800mm focal length. Orion nebula probably being one of them.
Ultimately, if you get into AP you're probably going to end up with a couple of scopes of different focal lengths for the different targets, it's just a question of what you pick first
