MCF8316A: Design Question

Hello,

I recently start my study of MCF8316A. I started by digesting tutorial videos in Precision Labs. However, I have a question from this tutorial material.

The video name is "4.2 Sensored vs. sensorless control", it mentioned the fan application could detect rotor's position by applying sensored/sensorless control.

My question is, what situation we determine to use sensored control or sensorless control in fan application? By judging fan's size? or cost? or other concern?

If there are any documents about this issue, please kindly provide me. 

Thank you.

James