It depends on the frequency of use and where the hand is typically located. The index and middle fingers are strongest, so the keys under them are the most valuable. I'm typically chording on the modifier keys and spacebar, so "v" and neighboring keys are quite valuable to me.

I agree that the default tool shortcuts in that area are somewhat wasted; Photoshop seems to have chosen shortcuts more for mnemonic value and got lucky with the Marquee tool forcing Move to the "v" key. Crop ("c") isn't needed with the same frequency as the drawing tools, and Zoom ("z") -- while useful for beginners -- is effectively unnecessary with the ctrl-space and ctrl-alt-space key chords. "x" (exchange foreground and background), however, is extremely useful e.g. for quickly switching between drawing and erasing on black-and-white drawings.