>>57892690They perform different roles. Latias is meant to act as a setup sweeper, whereas Latios is more prone to being built for immediate burst.
Gen 5 has both being equally broken with Soul Dew. Gen 6 has Latias fall off due to Xerneas and her type of role being harder to pull off. Gen 7 nerfed Soul Dew and required them to rely on their mega evolution, which before was entirely outclassed by Soul Dew. With this Mega Latias generally saw more success in both Gen 7 and Gen 8 Nat Dex, whereas Mega Latios is currently seeing more success in Gen 9 Nat Dex.
TLDR: Both are amazing for different reasons.
