One word: Haxorus.
It has a lot more attack and nearly the same speed. It can destroy with dragon claw and set up with dragon dance. So I would definitely go with Haxorus, but it’s your choice....
Nah, that attack is nearly Rayquaza level on Haxorus. Of course it’s Haxorus. I’ve used it in the battle tower before, and it can OHKO a ton of Pokemon. It even learns poison jab for fairies!
Flygon is good but not as good as Haxorus 100%.