Noivern VS Hydreigon!
VS 
1: Pros and Cons of Noivern
PROS:
- Good Movepool
- 123 Speed is excellent, so you do not need le Scarf. You can opt for le Specs so that you hit a lot harder.
- Infiltrator means that Sub strategies can't work against ze Noivern.
- Switcheroo in the Specs Set means that you can actually cripple walls forever.
- Moonlight (why it even learns it ? I dunno :D)
- Boomburst
- Bulkier than other Dragons, and not a joke
CONS:
- Useless abilities beside Infiltrator.
- Specs is mandatory if you need a special sweeper in Noivern.
- U-Turn, Dragon Claw, Acrobatics, Brick Break: this could end up in one of the best wallbreaker ... But 70 Base Attack.
2: Pros and Cons of Hydreigon
PROS:
- The most single diverse Pokémon ever. Access to Fire Blast, Surf, Dark Pulse, Elemental Fangs, Focus Blast, Charge Beam, Flash cannon and much more !
- Very Bulky for a sweeper
- Too fast for a tank
- A physical variant can be seen
- U-Turn is a great addition to its movepool
- Its goddamn too high special attack
- Can cover against each single type
- Good resistances ...
CONS:
- ... Florges
- Choice Scarf or too slow
3: The Choice
Hydreigon all the way. Except if your team is weak enough to Fairies, Hydreigon is better than Noivern, except in Speed. With a Scraf, you can make it up. If you really need Infiltrator, then Noivern's your guy.
Careful! If you are looking for a Dragon, then you might be surprised that Hydreigon is not quick enough. If it is a choice between the two, then Hydreigon.
