How many planets are there with over a million people, and how long does it take me to find them? I see it as kinda the same thing as the vampiric one with people, but on a larger scale. If I'm strapped for time every year so that I'm forced to eat good people, I say screw that. But if I just get to suck the souls out of a million demons or a Dick Cheney clone army, I have no problem with that. And the Power Cosmic kicks ass. AND there's no police force to chase after me... (I'm guessing I get to be Galactus level, but normal sized, right? I mean, if I end up being a jobber like Firelord, I'll take Flash anyway)
If I'd be eating a giant, tie dyed planets filled with psychadelic/good classic rock musicians, or if I'm turning into Firelord, I'd take the Flash powers. 1 second-25 minutes isn't terrible. (I think Flash should technically be something like 1 second=a couple thousand years) I'd just learn to talk really really really slow. And there is, of course, a HUGE number of other benefits that comes with being Flash...