Johnny Guest,
On the M11/9, the problem isn't so much the handle on top or side as the factory handle was so small, it literally hurt some folks fingers trying to pull it back.
Also, the handle on top went directly into the bolt, so it moved with the bolt. From what I have heard, the new design merely cocks the bolt and then returns to a rest position.
Like you said, mostly personal preference. I also allow plenty of cooling on all of my MGs when doing shooting session. While some may be designed to take the heat, no sense tempting fate.