I'm in the same boat with my M1A. Basically, for me it comes down to the fact that I have been on the fence about selling it for a while. And why not do it now while you can get a premium for it. If it's something you don't use, or if you have another project in mind to use the funds for, go ahead and sell it.
If your thinking you can jsut replace it later with another AR, then you should hang on to it.
Get a price in your head. If you can sell it for that price, go for it. If not, hold it. That's what I'm doing.