I think battery life is the most important. My Garmin Instinct 2 goes about 3.5 weeks between charging (the older non-OLED screen). It has solar, so I usually go over a month.

But a watch, something people will wear swimming, sweaty, in the rain, etc, is something that should ideally follow the wireless charging standards, and not have a plug taking up space, and being a spot for leaks...