Lebron is 6'8 and 250 pounds. He is the better athlete at every age. Lebron is the most perfect genetically engineered athlete ever.
Lebron could not stay with MJ though. MJ was faster, quicker and could jump higher. And do not underestimate Jordan‘s wiry strength.
Jordan played in an era when football was allowed... and heavy hand checking. The guy would easily average 50 today. Book it!