They both are good Pokemon, but I choose charizard because blaziken is not nearly as good without the DW ability speed boost.
Charizard Pros:
- Great movepool
Some moves are:
Outrage
Thunder punch
Iron tail
Shadow claw
Air slash
Flare blitz
Heat wave
Dragon pulse
(Not including TMs)
- Slightly higher defenses
- IT'S A FREAKING DRAGON!!
Cons:
- Stealth rock weakness
- Not quite as effective running mixed sets
Now for blaziken.
Pros:
- No stealth rock weakness
- Runs a good mixed set
- Higher both attacks
Cons:
- Pretty shallow movepool
- Lower speed
- No DW speed boost
So my recommended moveset for charizard is:
Charizard @ Life Orb
Ability: Blaze
EVs: 4 HP / 252 SpA / 252 Spd
Timid Nature
- Fire Blast
- Focus Blast
- Air Slash
- Roost
Hope I helped :)