We often work outdoors at parks because we vanlife. Think its worth the extra $300 mostly to get the brighter screen ? How is the MPA using it outdoors ? We always work in shade but there can often be glare.
The $300 is better spent enjoying life. Real-world testing shows minimal difference between the screens (both over perform Apple specs) and the difference is around 60 nits.
Depends on where you live. If you're in California or Florida it would make a difference. If you're in Alaska or certain parts of Canada, the system would be air-cooled just by being outside even in the middle of July and August.