I have some Arctic Cooling MX-4 in the mail and will apply and repeat the tests and post the results. AC MX-4 is suppose to be better than Arctic Silver 5, so I will find out.
I think MX-4 is a lot more versatile. It gives solid performance over a wide range of conditions. But if you're taking the extra steps that OP has taken to ensure that well-finished surfaces are meeting perfectly, it's still hard to beat AS-5. That said, there shouldn't much difference between compounds under those conditions. It's when dealing with various imperfections that some compounds will stand out more than others.
Shin Etsu grease is actually not that bad compared to the fancier greases you can purchase today.
You know, I really do agree with you here. Shin Etsu makes some pretty nice stuff. The syringe that you got from Apple is one of their X23 products, right? Do you know which one? X23-7783? X23-7762? X23-7921?
Is the stuff that you get in a syringe from Apple the same stuff that is used at the factory? Or is the factory stuff a cheaper version? Or is the factory stuff Shin Etsu at all? Does anyone know? It's the same color, but the texture seems odd to me.