It's impossible for me to recommend one over the other as they both have their own distinct advantages/disadvantages which will be rated differently by each individual rider, based upon their riding style and specific requirements.
If you enjoy pedalling, but would like
(or perhaps need) assistance on hills and into headwinds, then I would recommend the Smart Pie because it is smaller, lighter, less obvious and produces very little drag when the bike is being pedalled without motor assistance.
If you regularly have to climb steep hills, or are no longer able
(or just too lazy) to do a bit of pedalling to assist the motor, then I would recommend the Magic Pie, because the larger
(and more powerful) motor produces far more torque.
For most of my riding I tend to use my Smart Pie in preference to my Magic Pie, but I really notice the difference in power when riding up steep grassy fields. But when I want to have a go at pulling wheelies, the Magic Pie's superior torque makes it a lot easier
(which is also a lot more fun).
I hope this answers your question.
Alan
