(Happy New Year!)
Do these two sentences mean the same thing?
1) I wonder if X isn’t better than Y.
2) I wonder if X is better than Y.
On the surface, it’s a basic kind of statement (“I am comparing X and Y; X may be better, but I’m still thinking about it”) and they seem identical. At least superficially.
I think the sentences imply different things, though. 1) is something I would say after having already chosen Y, and then re-evaluating X. 2) can be said either before or after a choice is made, but seems slightly more natural to say before.
Then again, maybe sentence 1) is not quite Standard English and I’m just making all this up.