- Wong's figures with respect to ISD shield durability are correct relative to amount of energy in terms of photon torpedo equivalents. It's Wong's site, I think I can use his figures here without too much protest as to their unfairness, no?
- TOS era torpedos have a rated total yield equal to at least the "effective impact strength" considered for TNG torpedoes in Wong's comparison - i.e., the ~half strength given by an undirected radial explosion. Half strength TOS vs TNG torpedos may be a bit low, but let's run with it.
- The "energy equivalent of a torpedo" is its rated yield. Rather than theoretical potential, which could be quite a bit higher.
- Star Trek shields decline in a purely linear fashion with respect to input energy. Yes, I know the last 5-10% can seem to take forever to get rid of. That's dramatics for you..
- TOS Season 2 is canon material to use in determine the nature of Star Trek technology. Gene Roddenbury would say it's Star Trek - his fingerprints are all over it - and Paramount acknowledges it as a TV series and therefore canon. If TOS Season 2 is not canon, I'm not sure what is meant by the term.
Given this base set of assumptions, it is then possible to determine the relative strength of the shielding of a Constitution class vessel by the standard of the ISD. As it so happens, Episode #38 (TOS Season 2) provides a readily understandable measurement of the Constitution class's capacity for energy absorbtion through shielding. PT shall represent the energy yield of a TOS torpedo and the assumed "effective energy impact" (half yield) of a TNG torpedo (these were assumed equivalent above.)
Our shields absorbed energy equivalent to 90 of our photon torpedoes.
I may add the energy used repulsing this first attack reduced our shielding power 20%.
Shielding power is reduced by 20% with a single attack of 90 PT. Thus, an instantaneous attack of 450 PT should bring the shields down.
An ISD, as we know from Wong's calculations, requires (within the span of a half hour) 1000 PT to take its shields down.
Thus, on a single ship vs ship basis and taken on these five assumptions, it is not unreasonable to conclude that an ISD has stronger shields than the stock model Constitution class. Kirk would thus not win a toe to toe battle with an ISD on stronger shields, alas and alack.