I think losing grip on the front has been massively over-stated by many but I'm sure a light rider going up a steep hill with a powerful front hub motor may well lose grip especially on surfaces with poor grip for sure but for legal wattage ebikes I personally don't think its an issue. On some surfaces like sand where you have two powered wheels, rear powered by you and front powered by the motor grip can be improved. You can do a test though to see how good it will be on your bike before you fit a front hub motor. Go up a steep hill as fast as you can for a short spurt and then apply the front brake hard to see how much traction you have and if you skid. Ideally a situation where you have a nice flat run up to the hill to build up speed and then can start the hill at some speed as soon as you are going up the steep bit apply the front brake on its own as hard as possible. If you skid immediately then perhaps the weight balance on the bike or your lack of weight etc means it would be less than ideal to fit a front hub motor. I've also seen it written that for a e-mountain bike it is better to have a rear hub motor than a front hub motor and that maybe good advice overall but with a hardtail mountain bike where the rear of the mountain bike gets a lot of abuse and doesn't have any suspension to cushion the impact, rear hub motors especially direct drive can break a lot of spokes and have issues. So still seems less than ideal. If I wanted to configure a e-mountain bike and couldn't have a mid-drive motor I would probably have a smallish light geared hub motor on the front suspension forks. That goes against a lot of advice I'm sure but then I would be using the front hub motor to get me up the hill on the road or normal tracks before I then I would do the downhill technical course and could see that working quite well.
The advantages I see for front wheel drive;
1. Often on many bikes even aluminium frame bikes the front forks are steel so better for mounting a hub motor.
2. For heavy riders like me I get more punctures at the rear so prefer to have the motor at the front because its more difficult to remove to change tubes.
3. Again I'm more likely to be working on the rear wheel with regard cassettes, spoke replacements, bearings adjustment etc so prefer to have a easy to remove rear wheel.
4. Many cheaper rear hub motors have freewheel fittings and I wouldn't want that I want to use a stronger higher quality freehub on the rear wheel. You could argue that freehub rear motors aren't that much more expensive but then you have the extra complexity of a freehub ratchet system and the motor itself built into the same hub motor.
5. Not compromising the drivetrain options means I can have the exact gearing I want. Freewheels typically have a maximum range of about 14-34T which is very limiting for both high and low gearing.
6. Not much give in a hub motor rear wheel if fitted with a larger direct drive hub motor. They have short spokes and do not flex much they can feel a bit harsh unless you are using very thick tyres. I prefer the more springy wheel on the rear as aluminium frames are more harsh and prefer the harsher front hub motor on the front where the steel forks have more give. It feels the better combination.
7. Less of the weight of the rider is at the front which is why grip is slightly reduced but this means less load on the bearings and spokes which can make the motor last longer before attention.
8. If you wanted to return the bike to a conventional bike for perhaps a long distance ride or while you were servicing the hub motor you only have to swop back to your normal front wheel and take off the battery and most of the weight is gone.
9. Tyre wear seems to even out a lot more so you don't have to swop tyres as much between front and back to get even tyre wear.
10. I quite like the slightly heavier steering at the front for some reason, feels a bit more like a motor bike when you have a front direct drive motor hub.
11. Easier to repair punctures when you don't have all the gears in the way as well as the cables when removing the wheel to change the tube. In fact I would say it can even it out a bit.
12. Regen braking works better on the front in my opinion as remember when you are going downhill the weight now goes far more to the front of the bike, its the only time really when there is more weight on the front wheel so adds to traction. If you have the bike setup so that the rear brake lever activates regen braking then the first light pull causes the ebike to brake using the front hub motor which recovers energy but if you pull harder it then operates the rear physical brake where most of the riders weight is so the best grip and the best braking performance. If you are really in a situation where you have to brake even harder then obviously you can pull the front physical brake lever as well but I feel all you need is one lever braking 99% of the time and 95% of the time you don't need to activate physical brakes at all just regen braking which means longer range and zero wear to brake pads. It's always best to share braking between both wheels it reduces brake pad wear and tyre wear and its good for the structure of the frame and forks. You could of course argue to have regen braking on the rear and front wheel physical braking but to me that doesn't work quite as well.
