Marner's great ending to last season had little to do with linemates at even strength, as his production rate there was pretty much the same. He hit a hot streak driven by PP success, got a ton of minutes as a result, and kept on producing.
In any other case, I would take the guy with the superior performance in the better sample size over the guy with better performance in a smaller, more recent sample, especially when the latter comes with sustainability issues.
I don't get this. Matthews has a better case based on actual on-ice performance.