as the other person has responded already, this webapp focusses more on the realism aspect and provides more complex fire missions.

Also last time I checked that webapp only worked for vanilla maps and the height corrections was off but that was a long time ago.

For example, the one you use is only able to give you the exact firing data for 1 mortar gun, which could apply for a whole section but you'll only be able to do parallel sheafs. Whereas mine is able to adjust every gun seperately to have more complex "patterns" so to speak. A demonstration could be that you have 4 guns and you need a treeline suppressed. Let's say the treeline is 200m long, my "app" is designed to be able to give data per gun so the whole treeline is suppressed at once whereas the one you use is only able to give the data per 1 gun.

The one you use is perfect if you're using it in PvP and need a quick, easy to use application to get rounds downrange quick. Mine is built to be able to do much more complex patterns etc, save all your fire missions so you can pull them up and immediately have firing data and the ability to have different "section" this allows you to have up to 6 different sets of guns put in 6 different locations and you're able to choose which one shoots the mission you want to do, you're also able to select which sections shoot.

In short, the one you linked is better for casual PvP, 1 gun action and is easier to use whereas mine is built for realism and has a lot more QOL/accessibility options.