Questions regaurding the new MM motors??

[Desert Rc]

I need a couple new motors for my SCT trucks. I was going to buy my first MMP combo today and I was looking at the motor selection. I was going to run the newer version 4600 due to having so much heat with the 5700 in the same application. Now the new motors are the same efficiency wise just with new build characteristics or are they more efficient?? I just noticed they have the 9000kv WOW....this is what prompted my question. If I could run 3s on the 5700 without the heat of the older design that is what I would do.

I have to send in a new motor that took a crap on me after one run and a old MM so I will pay for the upgraded combo and will try another KV motor then...but I assume it will take a while for that to get back to my hands.

Any problems yet with the MMP that I have missed??