I have ridden in a hilly urban/suburban setting with as high as 82 gear inches (53X17), a norm of 72 gear inches (47X17), and, presently, for temporary health reasons, 58 gear inches (42X19).

Most of my rides involve a seven to 15 mile one-way trip, with a dynamic range of 800' (800' between highest and lowest points on the ride), but up and down that 800' more than once.

As I went to lower and lower gear inches, it surprised me how much my spin improved.
I no longer have a high speed bounce, and I find my spin limited only by my cardiovascular fitness (it takes energy to keep up with the pedals).

I found that my average times for each trip remained the same at every gear inch down to about 65 gear inches (42X17), and then, as I went lower, my total times began to increase, but not by much.

For a 7.5 mile trip through traffic with, typically, three stoplights, my time, whether at 82 gear inches or 65 gear inches, I averaged 26 minutes, with a one time, atypical 23 minute commute to work (just a good day, feeling my oats, enjoying a favorable wind, and hitting all the lights just right).

The same ride at 58 gear inches (42X19) averages 30 minutes, which means, going down from 82 gear inches to 58 gear inches added only four minutes to a 7.5 mile commute.

I think at the lower gear inches I can brake later, accelerate faster, and maintain a more consistent average speed.

I ride mostly with either a 17t EAI cog, or a 19t EAI cog.
Because I have a 130mm BCD crank, I can experiment with a broad range of inexpensive chain rings.
I have a 53t, 52t, 48t, 47t and 42t chain ring, and I learn a lot by experimenting with them.

In my humble opinion, 72.7 gear inches (47X17) represents the most useful all around gearing for moderately hilly terrain and minimal use or no use of brakes.

Factory street fixed gear bikes typically come with 78.8 gear inches (48X16).