For what you want to do, buy whichever is less costly.
That'll generally be QSUD, but current deals and the MIR on M1 may make M1 EP cheaper.
For the OCI you plan to run, either oil should be just fine.
Neither will likely be superior in your use, although M1 EP does have more Grp IV content without doubt, if that even matters.
Incidentally, a quick search of the UOA sub-forum will demonstrate that M1 EP is not a 15K oil in all applications.