To give you an idea in the difference between Apple's update and Samsung's.
Apple is updating to iOS9, all phones from the 4S, released Oct: 2011, to the 6S Plus.
A total of 11 models on 11 firmwares
If Apple push out another 7 updates in the coming year, that will be a total of 77 firmware updates.
Samsung is updating to Marshmallow, Galaxy S5, released Feb: 2014, to S7 (inc: Note, Edge, Edge +)
A total of 8 Galaxy models confirmed so far, and conservatively, around 3,000 firmwares for different CSC and Product codes for both unbranded and carrier branded phones on all variants.
If Samsung push out a similar number of updates, 7, as Apple, for each model, that is a total of 21,000 firmware updates.
(Galaxy S4, Alpha and Note 3 Marshmallow updates TBA)
For more information about phone models, variants, CSC and Product codes, see
42 Galaxy S5 models - Dummies Guide