They are the same combine except for the paint,go to a dealer and ask him what the differance is between a used C62 is and a 8680,then you will know what to buy,you will see the differance in resale value.
I am going to guess that the Massey has the highest resale value. It has been my experience with both Massey and Gleaner that most, if not all the buyers of the combines are previous owners of the same brand. An 8680 is going to have higher resale, because to previous Massey owners it is a much better machine than anything they have been used to. Most Gleaner owners have switched to the R series, so to them the C62 is a much tougher sale.
