It doesn't really matter at all I'd say. Because as long as you train the pokemon right you'll get your desired EV's. There are also Items that help EV growth* so you could catch a pokemon level 50 and as long as you only battle the pokemon that give you the specific EV's needed you'll be fine (say you wanted your infernape to be attack driven, then you could train it against a Gallade which gives 3 attack EV's + power brace = 12 EV's [and luckily there is a gallade in the platinum E4 :p]) Also Pokerus will give your pokemon extra EV growth, I've never had a pokerus pokemon so I couldn't tell you how it exactly affects EV growth but I think it doubles EV growth.
Sorry I got a bit carried away, but basically the answer to your question is no in my opinion :)
*Items = Power belt, power band, power anklet, power bracer. HP up, Protein, Iron , Carbos, Calcium, Zinc.