I have the Asus B850-I and so far have been happy with it. From the spec sheet I'd say :
Reason to get the B650-I :
- Cheaper
- Regular good-ol' threaded antenna connectors
Reason to get the B850-I :
- Wifi 7
- Higher (supposed) supported memory frequencies (not that it really matters)
- Clear CMOS on the back
- 4x fans/pump headers (3x on B650-I)
- One more ARGB (puke) connector (2x ARGB vs 1x ARGB + 1x DRGB on B650-I)
I picked the B850-I over the B650-I only because of the clear CMOS located on the IO shield side. That was the only relevant feature for me ... and maybe the additionnal fan header, but only needed 3 so far. Huge drawback for the B850-I are the small push connectors for the wireless antennas, makes finding 3rd party one a pain.