I don't really need the extra space, but I want to know if there would be a substantial enough speed difference to make getting the Pro worth it or not, or if a regular 840 would be better for what I want/need given that it is in-between the prices of the other two here.
I have an 80gb ssd for Windows 8. The OS uses about 40gb and, try as I might I CANNOT stop the drive filling with rubbish after 6months or so. There is so much data that dumps itself on the c drive that you cannot reasonably stop. Go for the bigger drive, in fact I'm swapping mine out this week for a 250gb and allowing a few key programes, PS / Lightroom etc, to install on the SSD.