J E,
Tensile strength and compressive strength are two different characteristics of materials, very much unrelated to one another in the science of strength of materials. I haven't researched the two separate values with respect to G-10 and aluminum, but they don't necessarily have any comparable meaning or relationship. Concrete has good compressive strength. Its tensile strength is useless.
Best is defined in many different ways. Strong enough is enough, once that concern has been met. Speedy's preference for G-10 is its lesser thermal expansion and contraction compared to aluminum. So if G-10 is strong enough, yet expands and contracts less - maybe G-10 IS actually taking the time to do it right the first time? It's not for sake of saving money or time. G-10 is more expensive. And the time allotted is identical.
The article Hired Gun posted the link to was dated April 2016, and Speedy is still using and prefers G-10 pillars. The prior article I'd read was dated years earlier. Are G-10 pillars going to compress/crush/collapse when encased in bedding compound, under a maximum 60 inch-lbs of action screw torque? Recognizing that the load is equally spread out across the surface area of the face of the action and the surface area of the one-piece trigger guard, rather than a concentrated point loading? We're not hitting them with a sludge hammer or shock loading with an impact wrench. 60 inch-lbs of torque - maximum.
I've used G-10 pillars one time in my life. I'm an engineer, not a gunsmith, but Speedy doesn't use anything else. "Best" and "finding the time to do it right the first time" are most often a by-product of multiple considerations - rather than a single determining factor. Nothing is added to the functional value of a pillar by using a pillar material with 4 times the required compressive strength - if the pillar material has other less desirable functional qualities.
Don't want you to get the idea you hurt my feelings or ego in any way, and I'm not carrying a chip on my shoulder. If it weren't for differing opinions, planet earth might not rotate. I'm expressing the considerations I evaluated prior to using G-10 pillars, which included more than strictly compressive strength. Honestly, the compressive strength concern was dismissed out-of-hand solely due to a well known gunsmith using and recommending G-10 pillars himself, and instructing gunsmithing students to use G-10 pillars during his classroom instruction. I'm not doing anything that hasn't already survived the test of time in Speedy's gunsmith business.