I went from 7 (on a 92 Paramount) to 10 (on a CF Motobecane )
9 is a huge step up and he 10 simply made it nicer
I also went from downtube to brifter
and from deep drop bars to a much shallower drop.
After 40 years with downtube shifters it's second nature shifting em so I didn't include them in making life easier.
The multiple cog allows for that close increment 'one step' that can make all the difference on a long ride into the wind or on steeply rolling terrain.
Becoming addicted to the one step, I've converted the Paramount to a 9 cog setup in the back (keeping the downtube shifting via a set of dura ace shifters)
I could have gone with brifters on the Paramount but all I really wanted was the easier gear selection and to eliminate the pain in the shoulder blade position the older bars gave on long rides.
I posted the two that made life easier for me.