On what planet is Cuddeyer or Hunter fielding, let alone hitting 20 HRs?
Of course a hitter putting up numbers in LF or SS is more valuable at SS. The question is, if you think Polanco is your SS, and you have Santana and no LF anywhere near the majors........are you really better getting a crappy old player for a year or two, or are you better trying Santana in LF?
IF Buxton puts up numbers like many think, those numbers work in LF/RF/DH even........so, if he was your LF, and Santana your CF, you'd all be "happy" with Santana's numbers.
Now, let's pretend you think Buxton is a better OF, so you move him to CF, and Santana to LF.....are you now unhappy with their offense, even though the defense is better?