Here are both product data sheets. They are very similar but I’d say not identical. Close enough for me though. I like Napa because they put their oil on sale very regularly and it’s a steal for $2.99 a quart. I’m running the 5w20 in one of my cars now.
I decided to call up Valvoline's tech line, and asked about the difference between the Maxlife Synthetic blend and the NAPA High Mileage. The guy on the phone said fairly assuredly there's less seal conditioner additives in the NAPA oil vs Maxlife, and if the Maxlife's been working for me to keep on using it. Also recommended based on our car's mileages (160 and 180K) to only use the Maxlife synthetic blend and not the full synthetic version.
That said, I'm trying to get my father's Kia on shorter OCIs, and NAPA was having a sale, and I bought him NAPA 5w30 Synthetic High Mileage. So for the next oil change in January or so, I plan to use that. Last oil change was the Valvoline Maxlife synthetic blend, since it seemed to use more oil with ST full synthetic and Royal Purple he used to run. It's cheap enough on sale most of the time that it might be a go to oil for a 4-5K OCI vs Supertech. It came to $17.50 with tax out the door.