I know what noneists and abstractionists say the difference is, I just don't grasp the difference. Noneism and abstractionism are two approaches to objects like numbers, fictional character, hypothetical objects that don't exist, etc. The basic problem is sentences like
(1) Sherlock Holmes smokes a pipe.
This sentence seems to be true, but how can it be true if Sherlock Holmes does not exist? A lot of philosophers deny that (1) is literally true; They explain why we agree with the sentence by some other criteria. Noneists and abstractionists both claim that (1) is literally true but they have different ways of explaining how it can be true.
The abstractionist says that Sherlock Holmes does exist, but only as an abstract object. That is, abstractionists distinguish between existence and actuality. Sherlock Holmes exists but is not actual. Sentence (1) is true because it makes non-actual claims about non-actual objects, but those claims are true.
The noneist claims that Sherlock Holmes does not exist but that there are things that don't exist and that there are true statements about those things.
Let's call statements about the ontological status of an object an ontological statement. Then the noneist and the abstractionist seem to disagree on ontological statements about fictional objects but agree on all other statements. I'm having a hard time seeing any real difference between these two views other than ontological terminology. What is the difference between saying that fictional objects aren't actual vs. saying they don't exist, if in both cases, the exact same set of non-ontological statements are true of those objects?