Geech,
The CMP is the best deal going on Genuine US made M1 rifles.
They are used, they have "been there, done that". Some are in better shape than others. All are parts mixmasters. All have been through 1 or 6 armory rebuilds in the last 50 to 60 years since they were made. Many parts may be original to the rifles manufacture date, but virtually all will have military repl parts on board in few or not so few numbers.
A "service Grade" is inspected and gauged to be in condition to issue to a soldier or marine about to need it in a big way. It will meet USGI armory spec of 4.0 MOA accuracy at 100 yds.
As received from the CMP the rifle may be relatively "dry" and just need a light cleaning, or it may be covered in grease and cosmo and need a full breakdown and solvent scrub before being lubed and reassembled. The wood may be relatively new if it's repl wood, or it may be the original with a lot of dings and oil soaking.
The Danes are US rifles loaned to Denmark in the early 50's then returned to the US when the Danes no longer needed them. These rifles will have Danish and Italian made replacement parts on them, which may include everything except the receiver. Don't worry though, the Danes & Iti's made EXCELLENT M1 parts. The Danes especially made some very accurate barrels.
Re the $100 price difference. Some people dont want foreign made parts on their rifles and the CMP priced them cheaper to enhance saleability as opposed to the all US parts rifles.
To see what the typical CMP rifles are like, go to:
www.swampworks.com/SwampysStuff-Home.html
You can see my entire CMP M1 collection....
Enjoy,
Swampy