The difference may be more in how they’re intended to be used rather than their relative strength. Conformal Coating Remover XT (part #2130) is slower evaporating so on larger surfaces it will probably be more effective. It will reside on the board longer and therefore able to soften, penetrate and lift coatings. Fast evaporators may not be as effective over larger areas because they would tend to evaporate too quickly and redeposit the coating. 2130 is also much lower toxicity, so safer to use when ventilation is poor. Fine-L-Kote Conformal Coating Remover (#2510) is faster and probably more tuned for smaller areas or spot removal, which is why it’s the formula offered in the pen.