I've never used 32s, but 28s, 25s and 23s, mostly the latter. Frankly, I can't tell much difference. I'm 195, pump 'em up pretty hard (120) and go. I ride lots of miles, but have never felt any kind of fatigue or pain I could associate with the tires.
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Truth is stranger than reality.
'96 Giant ATX 760 MTB
'01 Bianchi Eros
'05 Giant OCR Llimited Carbon Fiber + upgrades