The reason most of us refer to them as Heavy and Medium loads is to stay consistent with the WK terminology. The WK uses the same part numbers, but ARB calls them MD and HD due to the lighter weight for that platform.

XK Light load = WK Medium load
XK Medium load = WK Heavy load

For you I recommend going with the light load based off what you say you want. You'll see more than 1.25 lift and it will still be stiffer than stock. If you dont get enough height you can always add 1/2" via suspension spacers.