Balance is not as important as people think. Coin is the multiplier on the chest base value (or relative share of base value, if multiple pets opening). Agility is the amount of HP removed from a chest per second. When you multiply the two together, you get a (very large) number that represents their Coins-per-second. If you had two pets with same total stats (e.g. 5000/5000 and 2500/7500), the even statted pet would have higher product and therefore have higher CPS. But when total stats are not the same, it just depends on the math. For example, The gold computer (T16) is better than rainbow candy corn (T15), even though corn is closer to even, the computer just has more stats.
I think the misconception stems from the best pets in the game (currently) having even stats, but its not the even stats that makes them so good, just the crazy high stats in general. If next update had the legacy pet with stats 250000/500000 it would still be the best pet, despite having uneven stats.
Also, if you are not at pro level, then your pets will not be even statted, and the which one is better debate depends on play style. If you are active while playing, agility is probably better since you will break coins/chests faster, and it won’t feel boring. If you are a multitasker who just wants to open some big chests, do something else, come back later and repeat, coin is better. And of course which passes you have effects this as well.
OP: tough luck on opinions. Don’t know how you possibly thought you could avoid this.