To be sure the details that are visible with a 4" refractor are more subtle and difficult to see than when using the 12" Newtonian.
I am sure that some folks would look into the same eyepiece and say "there's nothing there". M51 does make a showier appearance in something like a Celestron 9.25 Edge or a Z12. It's very easy that way. Seeing the contrast differences in a 4" f11 refractor is more difficult and subtle, I grant. Same for the other objects.
Don't neglect the part of the system behind the eyepiece. Too often we make the discussion "all about the gear". The practice of observing skills allows the human to make the most of whatever gear you have, though. We shouldn't forget that.