I'd say it depends on your needs. Does the 318 have enough power to satisfy you? The 360 will certainly supply more low end and mid range grunt where you can use it.
Me personally I'd use the 360 every time,just for the extra cubes.
I was leaning towards the 360, just hurts knowing I built that 318 and it is just sitting there, hopefully will be able to sell it and recoup some of my cash from it, but you never get out of it what you put in it...Hmmm sounds like my last marriage..