yes direct drive is efficient at higher speeds but if you commute you most likely are changing speeds a lot. acceleration is not that great you need a lot more power and that means more weight and bigger batteries. you also have less gears so getting the right gear for your cadence will be very hard. I mean look at my Bosch bike I can cruise at 22 mph with a 36v 500 watt battery for 30 miles with some hills. Plus you don't have a torque sensor so peddling will never be as smooth or as controlled.
Wattage means little compared to torque for hill climbs. You can have a 1000 watt motor, if it's only putting out 30nm of torque it'll be useless for big hill climbs but will perform better as a mid drive. That said, most mid drives will out perform a hub drive but have a significantfly higher price if all other things (brakes, gears, suspension, frame, quality) are equal. There is also a much higher cost of maintenance as well as maintenance schedule. If you're staying mostly on the road, a mid drive might be overkill. If you're doing more true mountain biking, mid drive is the best option. I ride a 500 watt hub drive but I stay on the roads and trails. I will say my 500watt bike can handle the 1 mile long 17% grade I have to climb in order to get home. It won't do it on throttle only but with a little pedaling it makes quick work of it. I should mention my bike also has 24 speeds so that helps a lot.