Originally Posted by
Wilfire
World
WoD: 6 zones including a small playable area of Tanaan. Interesting, hidden and more importantly relevant treasures in every zone.
Legion: 5 zones including a small temporary area of Broken Shore + DH-exclusive Mardum. Boring, irrelevant treasures in every zone.
Classes
WoD: 11 well developed classes.
Legion: 11 watered down classes and 1 class that is an amalgamation of pruned abilities from other classes.
(here's an example of a watered down class: hunters used to have 4 defining characteristics: a pet, use of ranged weapons, use of traps and the ability to kite. Legion "trimmed" every spec until only one characteristic was left: pet for BM, ranged weapons for MM and traps for SV. Kiting was removed altogether by giving melee classes an obscene amount of gap closers and removing the need to kite in dungeons)
Garrison / Class hall
WoD: a highly customizable player home, 3 different classes of buildings (small, medium, large) each offering a unique way to interact with them and the environment. 20 (25) followers to send on diverse missions and periodic garrison invasions. Gave useful junk for your character.
Legion: a completely uncustomizable soviet era commune, 6 tiers of talents that hardly change how the class hall plays (with the exception of DH / DK / mage / warlock / paladin / warrior instant mission completion work orders). 5 champions to send on diverse missions. Gives useful junk for your character.
Quests
WoD: immersive, jaw-dropping questlines. Dailies replaced by high-level areas that offered unique and diverse ways of completing them (disrupting equipment, killing mobs / elites, transforming into mobs).
Legion: immersive, jaw-dropping questlines. Dailies replaced by scaled-up versions of the quests that you did while leveling, mostly of the kill x amount of mob y variety. Special shoutout for the world quest that has you chasing after squirrels.
Professions
WoD: useful, easily levelable professions that provided you with a way to make gold or improve your gear. Some offered useful QoL gimmicks (loot-a-rang etc).
Legion: mostly useless, hard to level professions that provide you with trash to channel into your obliterum forge. No new useful QoL gimmicks.
PvP
WoD: 2 new unique playgrounds for PvP players (Ashran and Highmaul Coliseum). Mostly balanced classes, with a few rare exceptions.
Legion: 2 new arenas that play just the same as old arenas. Broken classes.
Dungeons
WoD: 8 dungeons with 3 modes (normal, hc, challenge).
Legion: 10 dungeons with 3 modes (normal, hc, mythic (+). I wouldn't count mythic 0 as a separate mode since it is essentially hc.
Raids
WoD: 2 raids with 17 bosses available 3 weeks and 2 months after release respectively.
Legion: 2 raids with 17 bosses available 3 weeks and 4+ (?) months after release respectively.
Weapons
WoD: lots of different weapons, each of which had a sort of identity for different specs.
Legion: 36 different weapons that lock you into 1 spec.
Misc stuff
WoD and Legion have essentially the same amount of content available for fishing, archaeology and pet battle related stuff. Kosumoth the Hungered was found way faster than the Giant Wave Serpent, though.
Conclusion
While Legion has slightly more dungeon content, it has equal or less content than WoD in other areas.