Schwalbe Marathon Plus and Micheli Protek Max: what are the fundamental differences?
The actual differences would be known only to people who have been involved in product development or sales, and they would likely be under a NDA. So, let's speculate.


Weight: Both are very heavy tires, but Michelin is still heavier and Marathon Plus is known to have "good enough" puncture protection.
Construction quality: The only known fact about construction is that Protek Max has lower thread density than Marathon Plus (22 vs 67). Higher thread density usually means lower rolling resistance and smoother ride but is more expensive to produce.
Reputation: Marathon Plus is known to be durable and to have surprisingly low rolling resistance for that kind of puncture protection. Nobody knows about Michelin yet.


All together, Michelin has to compete with price if they want to sell at all.