well JOrgan uses java, and Grand Orgue can work with LInux, Windows or OSX. Grand Orgue is about a 600mb download. I think JOrgan is smaller.
some combinations of programs and computers work well, others don't. So unfortunately there is a learning curve involved with any new software.
I think Grand Orgue may be able to use Hauptw*rk Sample sets, Jorgan uses I think sound fonts.
AS it is that time of Year. Good wishes to everyone for the New Year !
regards Peter B