Salamence
- Excellent Attack
- Very respectable HP, Special Attack, and Speed
- Can learn moves like Fly, Strength, Dragon Claw, Earthquake, and Stone Edge
- Absolutely amazing Mega Evolution
- Two great Abilities
- Mega isn’t available until postgame
- Middling defenses
- Bagon is a bit rare and annoying to evolve
Garchomp
- Phenomenal Attack
- Above-average HP, Defense, and Speed
- Learns moves like Dragon Claw, Earthquake, Aqua Tail, and Poison Jab
- Decent Mega
- Mega Stone is hard to get
- The better Ability is the Hidden Ability
- You can’t even get it before defeating Groudon
Salamence is the better choice, due to it being more easily available.
Salamence @ anything
Ability: Intimidate
EVs: 252 Atk / 252 Spe / 4 HP
Jolly / Adamant Nature
- Dragon Claw
- Fly
- Earthquake
- Crunch
Hope I helped!