The Sub Pop version of The Wagon is 4:40 long while the Green Mind version is 4:53. I checked and this is how the two versions are credited.
Green Mind:
Don Flemming – guitar, backing vocals
Murph – Drums (credited on the single but not in liner notes of Green Mind)
Jay Spiegel – Toms
(I guess J didn’t want to credit himself but I believe he played guitar, bass and did the vocals on Green Mind)
Sub Pop Version:
J Mascis: guitar vocals
Murph: right drums
Jay Spiegel – left drums
Don Fleming: guitar, vocal
Donna Briddle: Bass
To me the Sub Pop version sounds a tiny bit faster and just sounds a little different to me for some reason or another.
I believe Better Than Gone is original. Don Fleming wrote it. He also played on that track along with The Wagon.
I know this is not a direct answer to your question but I hope it helps.