Chaox
Sees dead people
Towns Folk
I wouldn't say more than capable. If both players are equally skilled, you would need some luck to be able to beat an EV trained team. I'm not saying that its impossible. Just unlikely.
Again, I'm not saying that you need an EV trained team to beat another. Just that if during the battle your strategy (including your Pokemon types, move sets and abilities) don't give you an advantage over the opponent, its the EV that will make the difference. Even a slightly higher speed or attack can save you during the battle.
Out of all my friends, I'm the only one who uses actual strategy. That's why I don't have to bother with EVs/IVs when I play them. They more or less throw their Pokemon at me, then rage when I beat them using half of my team.