Focusing on the front or back powered wheel question, I prefer front wheel hub motors myself. I've tried several front and rear, but I go with the comments on here about better weight distribution.
I'm glad I don't have to decide on having a single bike, the compromises would make it a difficult choice. Thankfully, they're relatively cheap to buy (DIY conversions), small to store, and have no overhead running costs like tax and mot.
I'm not a power, offroad, or hillclimb enthusiast, so power and wheelspin on loose surfaces is not a problem for me. My cycling is country lanes and byways, and the newer generation of physically small front hub motors is ideal for my needs. Most of my bikes (and the recumbent trike) have Q100 front motors from BMS. They're not much bigger than dyno hubs, and very light, yet have plenty of power for me, as long as the right RPM for wheel size is selected.
I tried a 350 watt rear hub in my Giant Trance full sus bike, but it made it very tail heavy, and unwieldy on country paths, even when being pushed or manhandled.
Another consideration is the ease of puncture repairs. I found it much easier to do a roadside repair with a front hub motor than a rear hub motor. The combination of the weight, power cable, derailleur chain and torque arm can make removal and refitting tricky at the roadside, compared to an un-powered rear wheel and a straightforward front wheel motor.
All of my conversions have meaty torque arms, and I would imagine that forks, steering heads and bearings are built to withstand considerable forces from the riders weight during braking deceleration from the front wheel, greater than any loading from 15-20 mph front hub motors.