Good Questions Gab. This is based on my limited time with both setups.
Trails:
I did have my clyte 3540 hub on the Trek briefly and did take it on the trail also. My impressions of it on the trail was that it sucked. The rear tire felt really heavy. It made it hard to handle. The balance felt off and felt a lot of flex in rear. I Was concerned I was going to taco the rim after each time I hit the root. I was also concerned about getting a flat. I didn't want to deal with taking the torque arms off on the trails and disconnecting all the wires which are in electrical tape. The motor got hot real fast also.
The Mid Drive is definitely suited for the trails. The bike feels very balanced. Taking advantage of the gears was huge. I don't have a temp sensor on mid drive so can't tell how hot it's getting. But been running it pretty hard and no issues and motor cover feels warm. Never got hot to touch. One issue for me was it's more complicated. Figuring out which gear to be in on mid drive but that will come with time. Obviously, mid drives can be more prone to failure with all the moving parts.
Speed:
With no pedaling and on the streets, the hub was slightly slower. I would get around 30mph. With mid drive, max would be around 33. I think as you go up in power, the hub would be faster and drivetrain less of advantage.
Watts:
Sorry, didn't pay attention to this one.
Battery:
I can't really give a comparison because I didn't use the hub on the trail long enough. I do know that I ran a long time on mid drive. Considering all the torque involved with riding on the trails, I thought I would get only 2 hours but got double that.
Conclusion:
For trails, would not use hub motor. I would like to try one of those bigger hubs on the trail with big suspension and moped tires and lots of power like Stealth Bomber though. Maybe my opinion would change. But if you can't afford that, than mid drive is the way to go for trails for user on budget. For streets, the hub motor is my preference. I would hate riding mid drive on the streets. It's complicated and noise is loud (at least the cyclone). Mid drives also involve more complicated installation and maintenance. I like the simplicity of the hub. Obviously, lots of variables involved but this is my opinion.