Several of the guys I know own one or the other of these carbines. We had a discussion the other day as to what could be considered the more successful of the two. Considering the numbers manufactured and the worldwide employment of both over decades of service, I doubt that one could be considered a more successful design than the other.
As far as a very general conensus, the advantages of one over the other:
Accuracy: M1
Reliability under adverse conditions: unknown. (maybe SKS?)
Effectiveness of cartridge: SKS
Most produced: Unknown, since the SKS was produced in a number of different countries.
Ergonomics: I think the M1 got the nod here, for being more lightweight.
Durability: unknown, but the SKS is a pretty rugged design.
Effective range: SKS (?)
Ease of maintenance: None of us really knew if one was better than the other.
Other points: M1 has a greater magazine capacity
As stated, this was just a nothing-better-to-do-over-lunch discussion, so no really scientific comparisons. Opinions/thoughts?
