advokate
Hi,
short answer first: no, the battery performance of the Pixel 9 (Pro XL) is not better than its predecessor model Pixel 8 (Pro)!
I have these Pro models, but a comparison with the Non-Pro models is probably still possible and hopefully my experience will still be useful for you.
I guess, the Pixel 10 generation will be the first with real good battery life, if Google will give them the same or more battery capacity as the 8th and 9th generation have.
My tip for you and all other users of Pixel phones and bad battery experience:
If possible, use it at home with flight mode and WLAN.
If your service provider supports WiFi Calling, you can receive calls and text messages (!) in flight mode, if you set WiFi Calling (aka WLAN Call) as default.
This way my P8P battery lasts up to 100 hours at low usage, that's 1% every 80–100 min. in flight mode w/ WLAN on.
For comparison: with mobile radio but w/o WLAN, the battery of the P8P only lasts 72 hours with low usage.
BTW: I only use batteries between 30% and max. 80%, so I charge them up to max. 80% at 30% at the latest.
Conclusion: If you have a WLAN router at home or an older (spare) Smartphone, which you can use as WLAN hotspot (tethering), then you can save battery life of your Pixel phone.
And don't buy a Pixel 9 (Pro)(XL) only because of theoretical better battery capacity.