FWIW, I have seen many M1 Garands at the major Denver gun shows and several LGSs. I have also obtained 5 from CMP.
In general, Gun Show sellers offer rifles of unknown provenances, uncertain function and condition, and no warranty. Some friends have shown me theirs and most are misrepresented mixmasters, many having been put together by sellers. The same is true for LGS offerings who acquire them from sellers and traders. The prices for these guns are roughly twice what CMP would sell guns for or more.
By contrast, CMP clearly communicates their grade and stands behind their rifles...if the buyer has a problem, CMP solves it...and pays for shipping for resolution. I have been a CMP customer since 2007. Their rifles are accurately described as to condition and their customer service is as fine as any business in the industry. I have been to Anniston, AL to attend their Advanced Maintenance Class at which I built my Special Grade from refurb and reparkerized parts, a Criterion barrel, and a new CMP stock and stock metal. Their rifles are great shooters and well-priced. To me, the choice is obvious --- CMP.
YMMV, but I doubt it. Good luck,