I listen to local lossy music only, and I bought ZX507 for 4 reasons.
1. My new smartphone doesn't support SD card, so I needed a DAP.
2. It had to be Android, because I wanted to sync the playcount between the DAP and MusicBee on my PC.
3. I wanted to have balanced output. 2.5mm was okay but I preferred 4.4mm.
4. I wanted to give DSEE-HX a try.
That narrowed down to ZX507.
IMO ZX507's battery life is acceptable considering its tiny 1,500mAh battery, but I do hope future products would have at least 3,000mAh.
That's all valid reasons, for me wanting a device with the USB-C port on upper left side pretty much narrowed the choice down to the ZX-500 series....