Is it reasonable for an author to withdraw an accepted paper because they have since done better work? I submitted a paper to a good journal, it was refereed, and after a year it got accepted for publication.  

But now that a year has passed, I no longer find the results or methods of that paper to be that great (novel?). And much of my more recent work, which has been submitted to other good journals but has not yet been published, is of greater quality and improves on the earlier methods. 

Should I withdraw the paper, or just go ahead and publish it? To me it seems that there are negative consequences either way:


If the paper is published, then the readers may perceive the author to be shallow or inferior in some ways. Also, if the more recent work is published then people may think I'm over-using a particular method, or "salami slicing". Of course, the latter would not be accurate, as the most recent work was begun several months after the first paper was submitted.
If the paper is withdrawn, then the referee and editor (whom are very respected) may hold a grudge, or simply have a lesser opinion. That could impact future submissions and my reputation.




Although, if I formed a habit of submitting and withdrawing because of better and better results... my work would eventually be so wonderful that nobody would know about it!
No, this is not reasonable. It's up to you to determine that your paper meets an acceptable standard before you submit it, and stand by that determination unless you find a critical error in the work. Maybe it's not as good as what you're working on now, or maybe you're just overthinking things out of perfectionism, but it doesn't matter. Not every paper is a breakthrough, and that's alright.

Practically speaking, one less-than-exciting paper isn't going to give you a reputation as a salami slicer, and even if it did, this is much less bad (think several orders of magnitude less bad) than having a reputation for wasting editors' and referees' time because you won't stand behind your own work.

I'm not sure about the legal fine points, but you might not even be able to retract the paper at this stage without the editor's agreement (and why would the editor agree if there's nothing wrong with the paper?).