I would like pkmn at Lv.100, becasue the for each 4 ev points they get, one stat goes up by 1. (you put them in the box to raise the stats since they can't level up). Pkmn at lower level need more ev points to get one extra in a stat. To have a lv.5 is better in another way: You can learn it more and better techniques. A level 100 does not learn anything any more.
I would use the mew glitch rather than use a gameshark though, since I try to avoid cheating.
About EV (and that it's better at lv100):