Go for Fly, it can be handy for unexpected situations, for example Vs. Slaking. =) It can be also used to deal with those who use Protect most of the time, as we know protect can fail on its 2nd time of use. I used Fly to deal with a Yanmega using protect for speed boost on random match up. It can be also used to evade two turn attacks that needs to charge first like solarbeam.