In most countries e-bikes are limited to 250W and 25km/h, so considerably slower than what I do on my road bike with rim brakes. But your point still stands about weight. And if the e-bike is replacing other commuting, the weather will not always be nice which is another reason to use good disk brakes.
Yeah, I skipped on getting expensive Ultegra or extra light carbon frame, as I feel that don't really impact performance much. But I will definitely go for disk brakes next time. It's just smoother, and doesn't strain the hands as much when going down steep mountains. Even better performance as I with a disk brake bike dare to go faster because I know I can easily slow down before.
You are probably also right about the power, but from my workout yesterday my avg was 242 watts, and peak 686 w. So I still think it's about the same 8)
Take care though, hydraulic disc brakes doesn't always mean more stopping power. I found budget ebikes are mostly fitted with really cheap disk brakes that felt spongy and lacked safe stopping power. Good cable rim brakes are always better than cheapo hydraulic disc brakes.
