It is said that Darth Vader's body armour suit is a direct upgrade of how General Grievous was created. But I can't understand how this is an "upgrade". It was heavier, immobile (compared to Grievous), wasn't as agile, and as far as we knew from the movies it didn't have gadgets like grappling hooks, etc.
So why was it considered an upgrade? Surely the Grievous armour was a much better killing machine.