Without rehashing a lot of our discussion from the thread linked to above would add that the charts calculated above as with any gear calculator reflect the cadence range if the shifts are made exactly at the optimum points. In practice the shifts are generally made a little early or late and in our case with generally see about a maximum cadence jump of 7-10 rather than the calculated amount. When we do intervals on the flats there are times when we just can barely hold are speed at 90 cadence and a shift puts us close to 100 and the tired legs are spinning at there maximum. If we had a wider cassette we would have to slow slightly because we could not turn the bigger gear and would spin out in the smaller one.

Rather than thinking in the abstract I think the best idea is to try different cassettes with whatever crank you have double or triple. Assuming you are running 10 speed Shimano then buy a cheap Tiagra cassette or two in test configurations and see how you like the jumps. If you prefer a widely spaced cassette then you are a good candidate for a double and if you want a closely spaced cassette then you will most likely need a triple. There is just no substitute for seeing what you as a team actually like on your roads on your bike. After that is settled if you need to change cranks you can do so with confidence.

Tubrotandem and I have done that homework and like our respective set ups even though they are different.