So Fire types will have an advantage over Grass types but are weaker against Water types, for example
Dragons often have the 'flying' keyword, which means they can only be blocked by other creatures with flying or reach
The combination of first strike and deathtouch slaughters virtually any creature strategy while the combination of pressure and card advantage puts your opponent on the backfootespecially if you play this early with Llanowar Elves
Ignoring Condition: Even a rare card in poor condition will be worth less than a card in mint condition
Best guess is that someone at The Pokmon Company is a big Squirtle fan or something, because this already enormously powerful option is getting even more so with these eight extra cards
Theres a lot of established heuristics on this subject, and a few points I can toss in to help you construct an optimal mana base for Standard, Modern, Pioneer, or whatever MTG format you prefer