I'm building a new machine that will focus on CS6 media applications - photoshop, premiere, aftereffects, etc. I'm looking at two choices for my scratch disk - a 256 GB Samsung 840 Pro or a 600GB Western Digital Velociraptor (10,000 RPM/32GB cache)
Would there be enough of a performance improvement to opt for the smaller, but faster, SSD?
IMO it is worth using an SSD as a scratch disk for Adobe products, but I would suggest that you go with a Samsung 830 -- the small differences in performance are not worth the added cost of the 840 Pro, plus the 830 has a long history of reliability. Look for a sale coming up that should get you a 256Gb 830 for around $150.