What PSU tier list are you referring to?
Yes they are, Seasonic are among the best PSU manufacturers around (some would argue
the best) and their support is fantastic.
Put it this way also:
CoolerMaster MWE Warranty = 5 years.
Seasonic FOCUS Gold Plus = 10 years.
Realistically, you can tell a LOT about the quality of the PSU unit based on it's warranty. Anything 3 years and less is trash, anything below 5 is questionable. And 10 years+ is excellent, and you tend to only get this with the best manufacturers.
Someone will know more than me about the quality of the MWE Gold series, just
from what I recall, they're decent, but not fantastic. But I may be wrong. But I do know the Gold Series are definitely some of their better ones, so if the budget increase isn't worth it for the warranty and support alone, the MWE gold should still serve you well enough.
also they are both 80 plus Gold
Agreed - just be wary that 80 plus gold does say that the unit is probably better than other units, but doesn't necessarily reflect the overall quality of the components used within the unit. It is just more of an indicator.