are the CNC motors done from just one factory. They look identical to the ASG/Star wei/Magicbox ones. If you can output those for £40ish then I know exactly what my upgrade motors will be in the future!
Quite a few Chinese manufacturers are offering vented motor cans now. Not quite like ASG etc, still a number of differences like larger brushes, silver plated wire etc. Overall it's a step in the right direction at the lower end of motors.
It's possible, need to remember that the majority of motors (certainly Chinese) are all rated and tested at the factory for 8.4v, in airsoft we use them way past their designed voltage. Vents could perhaps mean the difference between fry and not fry at some of the extreme usage.