How does the 'Secret Wars' storyline from 2015 differ from the original 1984 'Secret Wars'?

The 2015 'Secret Wars' is a much larger and more complex event that deals with the collapse of the Marvel Multiverse. It features Doctor Doom as a key figure ruling over Battleworld, a composite planet made of different realities. The original 1984 'Secret Wars' was a more contained story focused on heroes and villains fighting on a single alien planet orchestrated by the Beyonder, with less emphasis on multiversal stakes.