What a fascinating discussion.
Putting everything together, the issue has not to do with the dimensions of the chain, whether 3/32 or 1/8, but rather whether the chain has bushings in addition to the rollers.
The high-end 1/8 chains have bushings and rollers.
Low-end 1/8 chains and most, if not all, 3/32 chains, have rollers but not bushings.
Check out the pictures and the discussions on these following sites provided by a major industrial roller chain manufacturer:
http://chain-guide.com/basics/1-1-1-...ion-chain.html
http://chain-guide.com/basics/1-1-4-...ain-parts.html
The 1/8 chains with bushings have the advantageous qualities of greater lateral stiffness, less internal friction, greater flexibility, greater resistance to shock and external wear, and greater resistance (when properly cleaned and lubricated) to internal wear.
However, 1/8 chains with bushings pay for their advantages with significantly greater weight, complexity and cost.
The question: how do the advantages of bushings compare to the light weight and low cost of bushingless chains; and, in terms of incremental improvements in quality associated with high-end track components added on to the advantages of bushings, will a perceptive rider notice a difference in performance, smoothness, control and confidence?
A Sugino 75 crank with a 43t Zen Messenger 1/8 chain ring and a 19t Phil 1/8 cog (I like prime numbers) will give me the same gear inches (about 60) I presently ride with a 3/32 drive system.
I can't imagine a quieter nor smoother drive system than the one I presently ride, but, I'd sure like to get rid of the slack in my present system.
I feel the slack, now, and it annoys me.
In the end, how much would I pay in weight and money to get rid of the 1/2" slack in my chain?