Minions do have vastly different stats and ability sets, but stat distribution is pretty zero sum. It isn't quite like triple triad where some cards are literally on a higher power level. I can't really think of any case where a particular minion has outright more stats than another. Different distributions? Yeah. One outweighing another outright? Nah. Some turn out better for actual pvp, but that's more of an emergent interaction between their statline and the metagame.
And it's actually the opposite. All the meta ones are free or easy to acquire, all the rare or real money acquired ones are garbage. Whether this was a deliberate decision or just plain luck I can't say, but it's what is the case so far.
