"Would you rather double your salary, or subtract as many minutes of your 5K or marathon time to get halfway to the WR?"
(credit Querfeldein) from the sub 17/six figure salary thread (http://www.letsrun.com/forum/flat_read.php?thread=4904593&page=1)
For me, I'd strongly consider taking the time. I'm in grad school right now, so if all goes well I'll more than double my salary once I graduate regardless. However as a current low 15s 5k guy with one 14:59 to my name, I'm sure that I'll never see the bright side of 14:00 or 2:20 unless I were quit science, put everything into running, and get extremely lucky. Dropping halfway to the WR would probably be much more life-changing to me than doubling my grad school stipend.
However, if it was a lifetime salary 2x multiplier, that would probably be a no-brainer. It'd be nice to guarantee that I could crack into the "not a f***ing billionaire" income bracket.