I don’t play OW, FPS isn’t my thing. But as far as I know Overwatch is basically a MOBA, an FPS MOBA, but still a MOBA.
I know OW has three roles (Tank, Damage and Support). And I was curious how different are OW heroes in these two games. Do they have the same roles? Do they have the same kit? How different are they in general?
I mean I know OW is an FPS, which makes it a 3D engine game, and HotS is essnecially a 2D engine game, so there has to be differences. But still, how large are they?
Well, first of all, Hanzo doesn’t have Scatter Arrow (W) in Overwatch because it was broken for OW, and his Dragon Arrow doesn’t exist.
His HotS’ (D) in OW is double-jump with dash into a direction instead.
Genji is almost the same, but his (W) and (D) work a bit different + he doesn’t have X-strike.
Mei is fully changed: first of all, she has Damage role in OW. In HotS her basic attacks is her RMB in OW; she doesn’t have LMB attack in HotS which freezes enemies in AoE; her Ice Wall in HotS also works different - in OW it’s just Tassadar’s (E) that has health. Her (W) in HotS is her Ultimate in OW. Her (Q) in HotS doesn’t even exist. Only her (D) is the same. Avalanche doesn’t exist .
Lucio also almost the same - he doesn’t have that (D) dash and High Five.
D’va doesn’t have these Pilot Mode abilities. Her Bunny Hop is actually emote in OW. Everything else is almost the same.
Ana’s AAs work different, but everything else is almost unchanged. She doesn’t have Eye of Horus in OW.
Zarya works almost the same too, but her Shields in OW work like Medivh’s instead. She doesn’t have Expulsion Zone.
Junkrat deals less damage in HotS, but his CC is better. Also his Riptire dies if he gets stunned, while in OW it doesn’t care.
Tracer doesn’t have lifesteal in OW; her Recall works a bit different; (W) is just a punch lol; Pulse Bomb surely deals less damage in HotS.
Did i miss anything?
Everyone but Mei 
is almost the same in OW.
Mei is a tank here and have a few different abilities than her kit in OW, while she’s an DPS hero.
Her Ice Wall elite ability is rather a normal skill in OW and her ice block/iceberg 
aswell.
She can freeze enemies in OW if she shoots her ice weapon on them for a long period of time. 
Every other hero from OW are pretty much the same, except they all got an alternative ultimate ability, along with their original from OW.
But I like that they did something different with Mei in HotS, making her more unique to this game instead of having the exact same from OW, its freashing. 
All OW heroes have their OW ult and an original one
For example Dragonstrike (OW) and Dragon arrow (HotS)
Lucio doesn’t have Push Off or High Five. Otherwise he’s very similar. Before Lucio was added to HotS, his aura was much larger but less powerful, but was reworked to a smaller, more contracted effect after his HotS release.
Ana’s Q is part her basic attack. Her shots either heal allies or damage and poison enemies. She doesn’t have lifesteal on Shrike either, and Eye of Horus isn’t a thing. She can however Aim Down Sights in Overwatch, so that’s accurate.
D.Va doesn’t have Big Shot, Bunny Hop, or any Pilot abilities. She can freely aim DM (rather than having to recast) and it destroys projectiles instead of reducing damage. Boosters lets her fly as well. Self Destruct is her ult while Micro Missiles is a basic ability that was added in a rework in Overwatch (why she didn’t have it originally).
Mei is a completely different hero in Overwatch. Her AA is a freezing mist that slows enemies and eventually stuns them, and her alt fire is a charged icicle that deals a lot of damage. Ice Wall is a basic ability and is a destructible wall that doesn’t have any CC. Her Ice Block makes her immune to damage, and Blizzard is her ult. Snowball Cannon, Snow Blind, and Icing were made up for HotS.
Tracer’s a pretty faithful 1 to 1, although her Pulse Bomb does a lot less damage here. She’s diverged a bit in updates, but is otherwise as close as you can get.
Hanzo and Genji’s traits work differently. Instead of a jump, both passively let them climb terrain. Genji also gets to double jump. So, they’re actually more mobile in HotS than Overwatch. X-Strike and Dragon’s Arrow were made up. Deflect also completely reflects projectiles rather than absorbing all damage and dealing a set amount.
I don’t have anything interesting to say about anyone else that hasn’t already been said.
In Overwatch, Junkrat can oneshot squishy heroes that get caught in his traps from any distance, and his riptire can climb up vertical surfaces in addition to being able to jump. He can also wind up riptire while suspended in the air. He has 2 charges of concussive mine. Also his trap and concussive mine can be destroyed when shot at.
Hanzo’s been updated in Overwatch since his inclusion in HotS, replacing his Scatter arrow which could oneshot almost anything if he aimed it at their feet. He now instead has an ability which quickly fire many arrows in rapid succession. He can also now dash every few moments in any direction.
D.Va’s Defense Matrix literally eats any and all things considered a projectile thus completely deleting them from existence if they are caught by it, including ultimates.
Genji’s Deflect works differently. Instead of protecting him from all damage, it completely makes any attack considered a projectile that hits it become his own and sends it back, but only from around the front of him. This includes ultimates. Ever had a Graviton Surge reflected back at you? He can do that.
Mei is completely and entirely different. She has a freeze ray as her basic shooting function that quickly slows enemies and then freezes them after a short period of continuous hits (basically a stun). From there she can deal immense damage by lining up easy headshots with her icicle secondary fire and is basically guaranteed to kill someone. Her icewall is also a basic ability which only acts as a wall and can be destroyed. Her AoE in HotS is her ultimate ability except much bigger and stuns longer. Her cryofreeze makes her invulnerable in addition to its other functionalities. She is not considered a tank and has much less HP than one.
Genji and hanzo can both can passively climb up vertical surfaces.
Ana is a full-fledged sniper that can heal from any distance she can see from. Though they generally stick with the team for protection.
Also in Overwatch, you can die from falling or being pushed off the map. It happens fairly often against certain heroes with knockback abilities.
“Armor” in Overwatch is not what it is here. Armor is a different type of HP that reduces a single instance of damage by a small flat number, but not below a minimum, which is highly effective against attacks with many instances of damage.
Some characters in Overwatch, like Zarya, also have additional shields as HP baseline. Shields in Overwatch regenerate over time.