They are both 9c motors. 3 or 4 different windings are available on the 9c. I would guess both companies offer a mid range winding. I have never ordered from Amped but I have ordered enough kits from Ebike kit to make it worthwhile for me to just go ahead and become a dealer.
The customer service is awesome. Shipping is always about $25 to get the box here to San Francisco.
In the box is:
a built wheel with freewheel (choose from 700c, 26, 24, 20), a thumb AND twist throttle, ebrake levers, sensorless 20 amp infineon controller, disk brake spacer( you may or may not need this), universal torque arm, hardware.
Amped bikes seems to offer the same motor and controller $80 cheaper but the plugs on the controller are garbage. Ask anyone here on ES who has built a few ebikes and you will learn that the plugs shown in the pic will need to be replaced if you hope to have a reliable bike. The ebike kit combines throttle and ebrake input into one plug , motor a second plug, battery a third plug, very slick see other pic. The plugs are more automotive grade not white chinese toy plugs, very important when you consider that full motor and battery power goes through these plugs.
Also Amped seems to only ship with 6 speed freewheel which could lead to buying and replacing the freewheel.
For the $80 savings you could redo the plugs. I don't feel like redoing a bunch of plugs so I always order from Ebike Kit