So I yanked the Hobbywing Fusion Pro out of my SCX10 Pro and put a brushed setup in to try out, it's a BR-XL w/ Crawlmaster Magnum Stubby 16t. I'll try to get it at an actual course this weekend to see how it does, but testing on some stuff at my house, it's kindof interesting.
The FOC basically seems to make the motor spin at a consistent RPM within the FOC range (0-25% with my tx), the transition out of FOC is a little abrupt feeling IMO compared to the Crawlmaster Mini, which I think has a wider useful range. When getting up onto obstacles and such, the FOC will tend to spin the wheels instead of the motor stalling out. I guess this could be a good thing or a bad thing, it's kindof nice to have them moving and can give you some control coming up over ledges and such. The downside is that it doesn't give you much traction feedback, it just breaks traction and there isn't much you can do to control that, because it's going to constantly scale up the power to keep from stalling or cogging. Once you break up over something, the car doesn't lurch and you can just kinda keep the same throttle input in without worrying about it taking off. I feel like the throttle curve is more gracious also and less touchy, but that's feasible because of FOC. The Fusion Pro also lets you run at a pretty low, slow speed, almost impractically slow.
The brushed setup I tested, on the other hand, stalls when it gets stuck and requires the user to add more power. It gives you some feedback when it's having trouble, so you can add more power and it will reasonably smoothly continue, but if you break over a ledge or something with it, it's gonna lurch forward, so you have to really be careful with your throttle input. The default curve on the BR-XL is also pretty touchy, but I think that is required given the lack of FOC or something similar. If you go from stuck to unstuck, it's gonna jump forward, so it gives you some feedback on what it is doing, but you really have to watch it, because it will punish you with speeding up too much if you aren't careful. The power from this motor is considerably stronger than the Fusion Pro though, in my observation, it almost feels like you could break the drivetrain with it. It gives more feedback but requires you to manage the power delivery to push over things. I can also run 4S, which is nice, and the top end power is a lot higher even at 3S, blipping the throttle makes it jump up onto things a lot better too. You have low end control here, but it's not going to creep as slowly and smoothly as the Fusion will. It starts moving at around 6-7% throttle for me, but it's not super smooth movement until 7-8%.
It almost seems like the brushed setup gave you more traction, where FOC will just keep pushing the motor until it either climbs or the wheels spin, the brushed setup will stall and let you slowly add power to bring it over the obstacle. The tradeoff is that if you just hold the same power setting, it's going to lurch and run away from you when it gets unstuck or the situation changes, so you have to be really aware of what it is doing. I think the question is whether the end user wants to control the throttle more or let the ESC manage it and accept the tires will spin if it gets hung up.
I'll try to run the same comp course I did last weekend to see how it compares. I think the question for me will be whether the potential for improved traction and feedback outweighs the downside of it being more error prone to operate.
EDIT: Oh and the overdrive seems to have an effect on it also, at 0% it operates a lot smoother than at 40%, at least on flat ground. Again that's at 6-7% throttle, when you start climbing over stuff, it doesn't seem to effect how smooth it is much.
