[Techhexium]

The sensors in a Lego motor are encoders, so saying that a Lego motor has a sensor is vague to people not as familiar as others to the subject. Lego Motors also feature PID Control algorithms.

I believe it's impossible to hardwire TETRIX motors to the NXT without the controller, and the TETRIX motors need a lot of power, and once the NXT battery runs out it takes 3-4 hours to recharge them back to full. The 10-cell battery needs only 20-30 min to recharge back to full.

In regards to the $80 HiTechnic controller, they are pretty expensive for what they do. But if you can get a FTC team to buy TETRIX parts for you they will receive a 30% discount so it costs only $55.

Finally, I want to point out that TETRIX motors have encoders as well, but a NXT and HiTechnic motor controller is needed to use it and the encoder cables are REALLY fragile anyway