There is an interesting thread in the UOA section of a GM 4.3 V-6 with a number of different runs using M1, PP, and Synpower, all in 5w30, as well as one run of T6.
The Synpower proved to be every bit the equal of M1 in terms of residual TBN, viscosity retention and wear metals as measured in the samples (not necessarily the same thing as actual wear).
Problem is, Synpower has recently been more expensive than M1.
Would I argue that Synpower did as well as M1 in this engine on 7K drains?
Yes.
Would I argue that it's the better oil?
No.
Still, there are a number of other good Synpower UOAs in that forum, so if Synpower would float your boat, use it.
Why would you consider using Synpower or any other pricey oil in your oil-swilling Saturn, though?
If the pickup has low consumption, then try Synpower in it.