To my understanding about the loot they will both drop the same sets except for hard/savage will have the dyeable version (if it's anything like the current dyeable gear then it'll also be a higher ilvl)

As far as difficulty I believe it was stated normal mode is for the casuals with an easy difficulty so that everyone can clear I think they mentioned something similar to like the Crystal Tower set of dungeons we have in terms of difficulty, but as far as the savage mode goes they stated itd be slightly more difficult than the current normal coil modes we have, but not as hard as the current savage modes