I read about this M1 conspiracy a while back, and decided to look at other oils. Using information gathered from the manufacturer's spec sheets, I put together a little chart tracking what I felt to be certain key properties and comparing them between M1 and the three underdogs. Here's the chart:
V@ indicates viscosity at the stated temperature. All else being equal, I prefer an oil with the lowest viscosity at low temp (to keep oil pressure manageable first thing on a cold morning) and with the highest viscosity when hot, to maintain good oil pressure when the engines' a blazin.
VI is Viscosity Index. All else being equal, a lower number is supposed to be better, though not even BobIsTheOilGuy seems to say why.
Pour and Flash are pretty self-evident. Lower is better for pour, higher is better for flash.
Of all the oils here, M1 0w40 has the highest viscosity at 100°C except for RedLine 10w40 and Amsoil AMO (both by ~ half a point) and those two have much higher viscosities at 40°.
Here's an interesting sidebar- Amsoil ACD is their diesel-rated 10w40. Its viscosity at 100° is more in line with a w30 oil, and it was only only Amsoil product I looked at which had no data at all on the HTHS 150° test.