Gear vs Stepper motor

[eschnou]

I'm finaly deciding myself to have a go at building my Cubetto (kids christmas is approaching :-) and looking through the docs I wondered about the motor choice.

I was surprised to see you are using gear motors for this project instead of stepper motor which would provide you the accuracy needed to have well calibrated turns and remove the need of the black/white bars hack (which is a really neat trick btw). Is it just a priced based decision or are there any other reasons ?

Instead of the opto sensors and bars, have you thought amout using a IMU ans small PID control to have precision turns ?

I'm tempted to go the gear motor + IMU route which seems cheaper and simpler. Plus an IMU could be interesting (detecting collisions etc.).