Sulfuric acid is H2SO4. Its fairly strong because the hydrogens readily disassociate from the sulphate group.
Sulphonic acid is an organic acid, with an organic molecule of varying sizes substituting for an OH group. So at best, its 1/2 the strength of sulfuric acid. The reality is that the polarity of the substituted organic group will have a large bearing on how acidic the new organic acid actually is. "Sulphonic" is just a generic name and doesn't provide much info in its potential acidity.
The free hydrogens are what lower the pH, create an "acid", and what attack and weaken the bonds in nylon. In any case, they are wildly different acids despite the similar sounding names.
Richard