The final slot on my competitive team; Azumarill or Mega Gyarados?

[Emboar]

After all the trading I've done, I've come up with a solid competitive team in Pokemon X. But, I wanted to know, should my last spot be Mega Gyarados or Azumarill? Their sets are as follows:

Adamant - Huge Power - Sitrus Berry
Belly Drum
Aqua Jet
Superpower
Play Rough

OR

Quirky - Intimidate - Gyaradosite
Earthquake
Dragon Dance
Ice Fang
Waterfall​

The rest of my team is:

Brave - Stance Change - Spooky Plate
Sacred Sword
Swords Dance
King's Shield
Shadow Sneak

Adamant - Inner Focus - Kangaskhanite
Sucker Punch
Power-Up Punch
Earthquake
Outrage

Quiet - Levitate - Roseli Berry
Psycho Shift
Thunderbolt
Psychic
Surf

Modest - Blaze - Charizardite Y
Fire Blast
Air Slash
Solar Beam
Dragon Pulse

Timid - Levitate - Gengarite
Shadow Ball
Sludge Wave
Confuse Ray
Thunderbolt​

Thanks!

 

[PlatinumDude]

You already have some Megas on the team, so Gyarados is out of the question. Just use Azumarill. Also, it's ideal to have only 1 Mega Pokemon on the team, as you can only Mega Evolve 1 Pokemon per battle. You'll have to decide on a Mega to use, then replace any Megas you don't want with Pokemon that fulfill similar roles to them.

Is this team for Battle Spot? If it's not, Aegislash and Mega Kangaskhan are banned to Ubers.

As tempting as Swords Dance + King's Shield Aegislash is, it's not worth using because it's easily walled and crippled by burn:
-Shadow Ball
-Shadow Sneak/Iron Head
-Iron Head/Pursuit
-King's Shield
Nature: Quiet
EVs: 244 HP/12 Def/252 SAtk
Item: Leftovers/Weakness Policy/Spooky Plate/Spell Tag

or
-Substitute
-Toxic
-King's Shield
-Shadow Ball
Nature: Modest
EVs: 244 HP/12 Def/252 SAtk
Item: Leftovers

or
-Shadow Ball
-Shadow Sneak
-Flash Cannon
-Pursuit
Nature: Hasty/Naive
EVs: 4 Atk/252 SAtk/252 Spe
Item: Life Orb

or
-Swords Dance
-Shadow Sneak
-Iron Head/Shadow Claw
-Head Smash/Shadow Claw
Nature: Adamant
EVs: 4 HP/252 Atk/252 Spe
Item: Life Orb

The lack of STAB seriously hurts on Mega Kangaskhan. Outrage is a bad option because it makes Kangaskhan Fairy and Steel bait. You're better off using Return for better neutral coverage; its other moves already handle Rocks and Steels:
-Fake Out/Power-Up Punch
-Return
-Sucker Punch
-Earthquake/Crunch
Nature: Adamant/Jolly
EVs: 252 Atk/4 Def/252 Spe
Item: Kangaskhanite
Ability: Scrappy

A Quiet nature is a waste on Latios, as its Speed is very good. If you can get a better Omega Ruby/Alpha Sapphire, that would be great:
-Draco Meteor
-Psyshock
-Surf/Hidden Power (Fighting)/Earthquake
-Roost/Defog
Nature: Timid
EVs: 252 SAtk/4 SDef/252 Spe
Item: Life Orb

or
-Draco Meteor
-Psyshock
-Hidden Power (Fighting)/Surf/Defog/Tailwind
-Trick
Nature: Timid
EVs: 252 SAtk/4 SDef/252 Spe
Item: Choice Scarf

Air Slash isn't worth using on Charizard Y because sun-boosted Fire Blasts out damage even targets that Air Slash would've hit for super effective damage:
-Fire Blast/Flamethrower
-Solar Beam
-Focus Blast
-Roost
Nature: Timid/Modest
EVs: 4 Def/252 SAtk/252 Spe
Item: Charizardite Y

Even though Gengar is frail, it can force switches very easily:
-Shadow Ball
-Sludge Wave/Sludge Bomb
-Focus Blast
-Destiny Bond/Taunt/Substitute
Nature: Timid
EVs: 252 SAtk/4 SDef/252 Spe
Item: Life Orb/Focus Sash/Black Sludge

or
-Substitute
-Shadow Ball
-Will-o-Wisp
-Taunt/Sludge Bomb/Sludge Wave/Disable
Nature: Timid
EVs: 28 HP/148 SAtk/80 SDef/252 Spe
Item: Black Sludge

or
-Hex
-Taunt
-Will-o-Wisp
-Sludge Wave/Sludge Bomb/Substitute
Nature: Timid
EVs: 8 HP/248 SAtk/252 Spe
Item: Black Sludge

 

[Emboar]

You already have some Megas on the team, so Gyarados is out of the question. Just use Azumarill. Also, it's ideal to have only 1 Mega Pokemon on the team, as you can only Mega Evolve 1 Pokemon per battle. You'll have to decide on a Mega to use, then replace any Megas you don't want with Pokemon that fulfill similar roles to them.

Is this team for Battle Spot? If it's not, Aegislash and Mega Kangaskhan are banned to Ubers.

As tempting as Swords Dance + King's Shield Aegislash is, it's not worth using because it's easily walled and crippled by burn:
-Shadow Ball
-Shadow Sneak/Iron Head
-Iron Head/Pursuit
-King's Shield
Nature: Quiet
EVs: 244 HP/12 Def/252 SAtk
Item: Leftovers/Weakness Policy/Spooky Plate/Spell Tag

or
-Substitute
-Toxic
-King's Shield
-Shadow Ball
Nature: Modest
EVs: 244 HP/12 Def/252 SAtk
Item: Leftovers

or
-Shadow Ball
-Shadow Sneak
-Flash Cannon
-Pursuit
Nature: Hasty/Naive
EVs: 4 Atk/252 SAtk/252 Spe
Item: Life Orb

or
-Swords Dance
-Shadow Sneak
-Iron Head/Shadow Claw
-Head Smash/Shadow Claw
Nature: Adamant
EVs: 4 HP/252 Atk/252 Spe
Item: Life Orb

The lack of STAB seriously hurts on Mega Kangaskhan. Outrage is a bad option because it makes Kangaskhan Fairy and Steel bait. You're better off using Return for better neutral coverage; its other moves already handle Rocks and Steels:
-Fake Out/Power-Up Punch
-Return
-Sucker Punch
-Earthquake/Crunch
Nature: Adamant/Jolly
EVs: 252 Atk/4 Def/252 Spe
Item: Kangaskhanite
Ability: Scrappy

A Quiet nature is a waste on Latios, as its Speed is very good. If you can get a better Omega Ruby/Alpha Sapphire, that would be great:
-Draco Meteor
-Psyshock
-Surf/Hidden Power (Fighting)/Earthquake
-Roost/Defog
Nature: Timid
EVs: 252 SAtk/4 SDef/252 Spe
Item: Life Orb

or
-Draco Meteor
-Psyshock
-Hidden Power (Fighting)/Surf/Defog/Tailwind
-Trick
Nature: Timid
EVs: 252 SAtk/4 SDef/252 Spe
Item: Choice Scarf

Air Slash isn't worth using on Charizard Y because sun-boosted Fire Blasts out damage even targets that Air Slash would've hit for super effective damage:
-Fire Blast/Flamethrower
-Solar Beam
-Focus Blast
-Roost
Nature: Timid/Modest
EVs: 4 Def/252 SAtk/252 Spe
Item: Charizardite Y

Even though Gengar is frail, it can force switches very easily:
-Shadow Ball
-Sludge Wave/Sludge Bomb
-Focus Blast
-Destiny Bond/Taunt/Substitute
Nature: Timid
EVs: 252 SAtk/4 SDef/252 Spe
Item: Life Orb/Focus Sash/Black Sludge

or
-Substitute
-Shadow Ball
-Will-o-Wisp
-Taunt/Sludge Bomb/Sludge Wave/Disable
Nature: Timid
EVs: 28 HP/148 SAtk/80 SDef/252 Spe
Item: Black Sludge

or
-Hex
-Taunt
-Will-o-Wisp
-Sludge Wave/Sludge Bomb/Substitute
Nature: Timid
EVs: 8 HP/248 SAtk/252 Spe
Item: Black Sludge

Thanks for the feedback, I've already started changing my movesets to some of the things you recommended. Also, this team is just for 6v6 battles versus some of my friends, and some occasional non-rated single battles at the Battle Spot. I can't do anything about the natures, as I want to keep this team all-shiny, as I didn't breed these Pokemon, they're just from trades, so I can't really get these same shinies with better natures.