If you have a level 99 Pichu that was properly EV, then you evolve it into Pikachu at level 100, it would have stats.

If you have a level 1 Pichu that you EV train and which evolves at level 2, then you continue the EV training, then raise da new Pikachu to level 100, **then the 2 Pikachu, if both have the same EV and IV, would have the exact same stats.**

Now if you evolve one into Raichu, then Raichu would be stronger than Pikachu. If both become Raichu, then your Raichu would be the same.

Is it trick ? :D

Hope it help.