I don't understand why anyone would want to buy gold over the steam edition. I've seen a lot of people on twitch talking about how they want to buy FSX but don't want to go with steam and instead get the boxed version of gold. Steam Edition is gold, but bug fixed and continuing to be patched by dovetail.
In terms of price, on amazon.co.uk the box version is selling used for £92 and new for £125 (Click here)
so for the price of getting the boxed gold version you can get steam edition (£19.99) Orbx Global (£53.81) and Global Vector (£37.66) spending £111.46. You have have spent less than buying the boxed version of the game new, have massively better textures than you would get in the gold version of the game and still have some change to play around with to spend on maybe other add-on, an airport or something depending?
So personally if you don't already own the game just save yourself money, get the steam edition of the game enjoy the add-ons that do work and a lot of them do and wait for add-on like active sky next and PMDG aircraft.