While I agree with Cruiser in this case, it doesn't seem like a K would really benefit him in the low altitudes of Illinois; BUT, I have to stick up for the mighty 231 in a few things...
1: The turbo is not a handicap below 15,000. A 231 will outrun a 201 at most altitudes, with the big difference starting above 10,000. Yes, you'll burn more fuel and the 201 is more efficient, below 10,000.
2: In this case, it sounds like the 201s are better equipped, but on average, the 231 came with more standard equipment, such as oxygen, folding rear seats, one piece belly, long range tanks, etc.
3: No, it isn't 1/3 more fuel...more like 1/4 (But yes, more fuel burn, less efficient)
4: Don't underestimate the value of a turbo for high density altitude days. While I routinely use high altitude airports so I really get the turbo benefit, it could also help on a hot and humid Illinois summer day too.
So, in conclusion, 231s are great. If you disagree, you're entitled to your wrong opinion