And your least?
Favorite: Legion, I can get to level 30 in High Mountain pretty easily if you kill rares/loot chests. You also get the class hall going for some of the exclusives for classes.
Least Favorite: Classic Zones, I finished all of Durotar and barely cracked level 20. The story is basic because it’s just an introduction to the Cataclysm/orcs/trolls. Not many good rewards at all.
Legion for sure. Second best leveling zones in the game.
Cataclysm/Classic.
There are just so many more zones to choose from compared to every other expansion. I get bored really easily so I just do one until I’m bored then go to another. Also when you’re leveling by dungeon finder you aren’t doing the same 5 dungeons over and over again.
Loooove legion. Was my favorite xpac and such a fun time to level. Even without flying!
Least: Honestly any content before MoP. Thought I loved it for the lore, but it is SO freakin slow!!!
I wanna say MoP, but I actually have a hard time leveling there, as it makes me all nostalgic and sad that that was the last truly good expansion.
WoD is a favorite of mine to level in. It had some pretty nice zones.
Most favorite is Cata if dungeon spamming or Legion/WoD for questing.
My least favorite, by far, is BC. The quests are the last vestiges of Vanilla quest design where drop rates can be absurd and quests are all over the place (but at least not as bad as OG Vanilla).
As someone who has done it all far too many times, I value nothing but speed/efficiency.
Wrath.
That dark, frosty Wrath feel… 
Those frosty blue Nexus vibes… 
Favorite: Pandaria. I personally really enjoyed the story for each zone.
Least: Classic. It’s just so boring.
WoD felt pretty quick when it came to levelling fairly easy to travel though as well. Though i think they nerfed the XP in the Bonus zones, those used to give a ton of xp.
I do WoD. Gotta get that free garrison. Plus, the last time I looked, it’s one of the fastest expacs to level in.
I will sometimes do Cata if I want WoW to chill/study/relax to.
In all seriousness, I really like questing. So Cata/TBC/Wrath all give a really long questing experience if that’s what I am looking to do. It all depends on what I am using the Alt for. If I just want Speed then WoD/Legion is good (Although I usually go with WoD because I am a RTS nerd so a free base is hard to turn down, it gives me WC vibes), if I want to chill and just enjoy some roleplaying then the older expansions are good. I even did Mists once when I had a monk I was working on. The one expansion I don’t want to do is BFA, the story in that expac is just too terrible, I also don’t see me ever doing Shadowlands again when we move to DF.
Its between WoD and Legion. Those were “peak WoW” in terms of the narrative vibes.
TBC is awesome in terms of zones but narratively barebones and WOTLK… no. Knock-off Vader twirling his mustache is not how I remember my King.
It’s funny to me, Gul’dan is an alternate timeline character and he’s one of the greatest villains in the franchise in my opinion. He just works so well. He’s got that Dr. Evil vibe but he’s not so clingy like LK.
I’ve been leveling through the BFA zones but remain in Wrath Chromie time for the random dungeons (along with a bit of dabbling in Draenor for rares and bonus exp hubs).
Super fast.
The fact that we are even able to discuss “What flavor of WoW do you play?” is really cool and something unique retail has over classic. I do wish it had a little bit more fine tuning.
Maybe a few more options could be added. Like if there was some menu where you could tune your leveling down to something more appropriate for when the expac is out, or if there was an easy to select option to keep your character in the expansion until you were ready to leave. I know there is a way to turn off experience, but it would be nice if there were some some easy to select options from a menu on the UI to customize your experience.
I don’t want the way we level to get dropped in the future, like blizzard tends to do with various systems. I want them to keep improving it, because I think it’s really fun.
I’ve run into two quests that the scaling doesn’t work at all and the mobs wreck you. One in Durotar in the cave NE of Razor Hill. The Burning Blade in there have a spell that’ll almost one shot you.
The other is one of the Magnataur quests in Dragonblight.
You might want to send in a ticket for those.
Yeah, that happens to me too. I forget what quest, but there is a quest in WoD where a dude hulks out and totally just destroys me every time.
It isn’t as bad, because it’s still beatable. Still, it’s always a sobering experience. It makes me feel like The Punisher when he gets destroyed by The Russian in the old Punisher movie.
When you run into a quest with bad scaling:
Oh, they’ve been ticketed many times. This has been going on for a while with those. You can even read the WoWhead comments. And yes, one of those tickets were mine.
They don’t care.
“Check wowhead.”
Favorite: Cataclysm/Classic
So many of the zones have interesting storylines. I don’t even care about the leveling speed anymore, I just want to enjoy the lore.
For instance: Badlands, it’s a sad story with a little comic relief from “I punched Deathwing in the face!”. That and Stonetalon is sad as well, but with some justice from Garrosh.
Least favorite: Burning Crusade, simply put because the zones are huge, and it’s dull. Hellfire puts me to sleep and Shadowmoon is (for lack of a better word “ugly”). Pandaria is right behind it though, since the SI:7 quests are bugged and can’t do them.
Classic for all those low level dungeons full of quests.
Otherwise, I pvp for levels like a real worgen.