Both are Valvoline full synthetic oils rated SN and A3/B4
MaxLife , SynPower
KV100 14.4 , 13.4 cSt
TBN 11.3 , 11.4
Noack 11.3 , 10.6 %
Mo 137 , 0 ppm
Zn 1036 , 983 ppm
Ca 3135 , 3159 ppm
The SynPower has the Noack volatility advantage, which is probably the reason why the MaxLife is only MB229.3 as it doesn't quite make the 10% cut-off (with rounding). But the MaxLife has a good dose of Moly which is not present in the SynPower. In all other ways they look fairly equivalent to me.
I would happily use either and buy on price. At the same price, I would go the MaxLife.
I happen to be using SynPower 0W40 right now, but we don't get those full synthetic MaxLife oils in Oz. I wish we got that ML here.