Sorry to say, but none
The Charizard's are very bad in the Dex of the National Variety and would be outclassed endlessly by Rayquaza-Mega (and more actually, but her as a Mega, or even Gengar-Mega, but for starters, you'll not be using her (Gengar) much). There are legit 0 teams in which you'll be choosing the former than the latter. Rayquaza-Mega has the following benefits over Charizard-Mega-X and Mega-Y:
Ability to hold an item
This is actually huge. Very huge. She can hold legit anything and almost everything, from Choice items to Life Orb. This means that she automatically gets a power boost, turning 3HKO’s into 2HKO’s, and even some 2HKO’s to OHKO’s after some chip through Rocks or something. Charizard-Mega-X and Y are limited to their Mega Stone, which is meh, and they’re weak as bleep already lol.
Better Ability and Stats
oml rayquaza do be having 180/180 and a bleep ing fast speed too oml omfg omg :OOOO :0000 nyaa uwu owo :ppp:333:3oml nyaayayyanyyany furry owo uwu
In all seriousness, Rayquaza-Mega has a better ability and better overall stats. Even though Tough Claws is good enough, it'd struggle to break past things like Arceus-Ground and all, which'll wall it endlessly. Charizard-Mega-Y's ability is dogshit where you'll be seeing things like Omega and Alpha weathers, and Delta Stream. Stats, do I have to say anything lol?
Easier to fit on teams of almost every archetype
Rayquaza-Mega doesn't have any issue about being fitted onto any team (which isn't Stall), so it's all g here. You'll be doing her on 3/4th's of your teams, if not more. The ability to defeat it's dedicated checks after a boost/whatever is huge too.
So the main thing is, they're both outclassed by the greatest Dragon, Ms. Rayquaza-Mega, as a Mega.
Ummmmmm that's because I wanna choose a lead Pokemon for my team and as the rule goes I love Charizard much more than the legendary groudon that's it
commented 16 hours ago by Themaskofdharma
gasp oml dies of shock jesus takes a pencillin christ swears a little goes to a temple and starts praying dies of shock again jesus christ
Mate, if you don't wanna use the so-called "legends", please don't play NDAG! Charizard is, currently, one of the best Pokémon in Gen 8 PU. The Charizard Mega's both have a niche in Gen 7 and Gen 6 OU. All three of these formats, especially Gen 8 PU, have a lot less "legends" than NDAG. Legend is just a classification. Granted, they have better stats, but please don't refrain from using them in a tier where, if you don't use them, you'll get a LOT less wins.
Hope it helped, and yeah try to adhere to the small piece of advice in the end.