Started a new game in White for the heck of it.
The Oshawott I first picked got +3 HP, +2 ATK, +2 DEF, +2 SP.ATK, +1 SP.DEF, +1 SPD on its first level-up. However, it had a Docile nature (no effect on stats), so I reset for a better one. This second Oshawott had a Naughty nature (+ATK/-SP.DEF), but its stats increased by only one point each when it grew a level. Did I make a boo-boo by choosing the second one? And generally speaking, which is more important: Good IVs or a beneficial nature?
EDIT: I just remembered one of the reasons why I quit playing White: The encounter rate is almost unbearable. Hopefully they'll tone it down in BW2.