Having built both, actually I'm just building the Aurora at present I would rate them fairly equal in difficulty. With the Warrior the biggest thing for me was setting the angles on the the front wheel booms and of course building the wheels. For that I kinda cheated by asking my LBS to order rim's, hub's and spokes and also lace them up. With the Aurora kinda the same issue only with the rear wheels. I copied the hub pattern of the Warrior front wheels and then recycled the Warrior's rim's. The biggest issue after that has been minimizing welding distortion and making sure the frame is nice and straight. Not impossible but fairly picky. I'm just shy of 200 lbs and do use e assist so have selected a bit thicker frame for the Aurora having bent the Warrior's frame a couple time's.