>>19874587Given that speed determines turn order, it's significant to at least some degree.
For example, say you had a 252HP/252Atk/4SDef Mega Mawile out against a 252HP/252Atk/4Spe Tyranitar, neither of which have speed investment.
Being naturally faster, the Tyranitar could attack Mawile first, taking 67.1 - 78.9 of its health out with an Earthquake before Mawile could KO with Play Rough. However, if Mawile had enough speed investment to outspeed neutral-nature 4 Speed Tyranitar (96 EVs, giving a spread like 164HP/252Atk/96Spe), it could Play Rough first and KO Tyranitar before it could attack, saving the Mawile from considerably damage.
Of course, the standard M-Mawile spread is something like 132HP/252Atk/124Spe, so slower Tyranitar would be unlikely to stay in unless their trainers were making some risky predictions.
