To the best of my knowledge Green Stuff pads were aimed at the "spirited driving" and "track day" drivers.
If you do any track days then they may offer some slight advantage in terms of brake fade, however the majority of Morgan trads are well braked and if you suffer brake fade on the public roads I might suggest that you are driving a tad irresponsibly.
As others have said , they do produce a lot more brake dust, so this might sway your decision if you have wire wheels.
