Like a lot of people, I loved the Mach Bike's speed. I am was really impatient so the Acro Bike never had a chance. Like OP, a lot of my time was spent hatching eggs so the speed was nice to have. The Acro Bike's tricks were kind of cool though.
I loved the Mach Bike, I remember as a kid I spent a lot of time racing through the Cycling Road, trying to beat my personal best time.