I use a mix of both in my 1 hour maximum commute context.

The USB devices are generally brighter, which must be due to the higher voltage battery (over 5V versus about 3V for two rechargeables). However all of them turn off abruptly when discharged whereas the rechargeable AA and AAA lights just get dimmer. I like having at least one rear light that will give some level of glow…so I don’t go completely ninja.

Though not a rear light, my all time favorite bike light is the discontinued Philips Safelite. It is USB charged but the 4 in-series batteries are standard AA form. I’ve replaced the batteries on mine twice. The aluminum case is a Sherman tank.