It doesn't make any difference. In order for a product to carry the "Dexron III" label it must pass a very comprehensive series of tests, and only a very narrow range of base stock and additive package will pass all the tests.

If you had access to each brand's certification test results you might be able to sort through it and find a brand that exceeds the test requirments more than any other, but whether it is "better" would take real world testing.

Anyone who claims their brand is best is just regurgitating marketing hype. The same applies to motor oil and most other automotive fluids.

Duke