Are there any inherent differences between a Visa credit card and a Mastercard credit card?

Obviously, there can be huge differences between one Visa card and another. And between one Mastercard and another. But I am wondering about any significant categorical differences between the two major types of credit card.

Perhaps, hypothetically, Mastercard always charges merchants an extra percentage point? Perhaps Mastercard travel reward cards are always better than Visa travel reward cards? Or perhaps there's no real categorical difference.