I too entertained the idea of the PixelBook but just this week I sold my 2017 15" MacBook Pro and bought a 2015. I couldn't care less about the TouchBar but there are some serious reliability problems with the butterfly keyboard.
What I liked about the 2017:
- Great screen (the P3 does make a difference).
- Loud speakers (though over a certain percent the chassis would vibrate).
- Slightly smaller footprint.
- Slightly thinner.
- Weighs slightly less.
What I like about the 2015:
- Reliable keyboard.
- Stiffer LCD hinge (less wobbling, don't care about how hard it is to open).
- No branding at the bottom of screen.
- MagSafe power adapter with charging/charged LED status indicator.
- Storage can be self-upgraded.
- No accidental TouchBar taps resulting in play/pause or locking screen.