Erm.... OK, time to bust the myths of the myth-buster. I agree with some of the assertions, but:

1) When comparing equivalent tire and wheel types, small wheels are undoubtedly harsher (and faster) than larger wheels. Even wider tires (e.g. 1.75" 406's) tend to be harsher than larger sizes at the same PSI's.

BTW put in another vote for doing a test on potholes. They're hard on an unsuspended 700c bike but unbearable on 20", as I found out in Belgium....

2) Anything you can think of to make a small tire / wheel more comfortable can also be done with 26" and 700c, with an equivalent effect on performance. As a result, I suggest you compare apples to apples rather than modify various parameters.

3) Bike weight, especially non-rotating weight, has almost no effect on performance. Aerodynamics, rider position, and drive train efficiency are more important. E.g. TT bikes and recumbents are both heavier and faster than standard bikes. Similarly aero, trispoke and disc wheels are heavier than traditional wheel designs but, in many circumstances, are significantly faster.

4) I have never heard anyone suggest that smaller wheels are weaker. It's pretty well known and understood that smaller wheels are stronger.

5) Smaller wheels undoubtedly have more responsive handling than larger wheels. In most cases, viewing this as a pro or con is a matter of personal taste; however I've found it extremely difficult to do hand signals on fast club rides with 20" wheeled bikes while maintaining good control. It'd be irrelevant for slow or solo rides.

By the way, if it was possible to set up a 20" bike with the same handling characteristics as a 700c, someone would have done so by now and trumpeted it in their marketing materials.

6) Wider and lower-pressure tires definitely have higher rolling resistance; wider tires also have more drag. Ergo wider + lower psi = worse performance. There are some exceptions based on designs and casings, notably the Big Apples.

7) There is absolutely no question that wider tires are available for 26" and 700c bikes; it's only racing-style road bikes that tend to limit tire size. Typical hybrids will run 32c's, my cross can take up to 40c, Surly even makes a 26" wheel that's 65mm (!) wide for its Pugsley.

To suggest that wide tires are somehow unavailable in 700c is incorrect. There are far, far more tire options in 700c than for 451, 406 or other small sizes.