Just a scenario... Say you were Rogue and you had gone evil and decided to go on a rampage. You're staying at the X Mansion and the following X-Men members (I know they're not current) are also staying there:
-Jean Grey (not Phoenix)
You only have enough time to drain the powers of 3 of them before all of the remaining members are awoken (whoever you drain will also be out the fight). Which 3 do you drain to give yourself the best chance of defeating the rest?