Hi Luigi and
to the forum.
The Magic Pie has a fair amount of dynamic drag due to the large number of magnets combined with the large motor diameter.
On the level, I only really notice a difference at speeds above 8~10mph
(12~16km/h), but on hills, you will instantly notice the extra pedal force required to overcome the additional weight of the motor and battery etc. at lower speds.
The Smart Pie is smaller, lighter and cheaper and does not have anywhere near the amount of residual drag that is experienced with the magic Pie
, but it also less powerful and does not have the tremendous torque that the Magic Pie produces.
If you do a lot of pedalling and just want additional assistance with headwinds, steep hills or long inclines etc. then the Smart Pie may be adequate for your needs.
If you want a motor that will be able to power you up most hills without having to pedal, then the Magic Pie would be a better choice.
My only concern with the Magic Pie would be the possibility of wheelspin on an incline under load as the downwards force acting upon the front driving wheel would vary considerably with each rotation of your arms if you were working hard
(unless you had a Tadpole trike fitted with a rear motor).
As far as the top speed on the level is concerned, it should be pretty much the same for both motors.
Alan