For me, I think 48-32 hits the sweet spot.
My bike was originally fitted with 52-36 with an 11-28 cassette. The 52 is great for the fast Sunday club rides, but I noticed on hilly audax rides (or one with plenty of rolling elevation) I tended to stick to the small ring. But I kept cross-chaining 36-11 as a result so kept shifting between big and small rings. That got annoying.
So I switched to a 53-39 in front and an 11-32 at the back, which roughly retains both high and low ends. I figure for randonneuring I would be able stick onto that 39 better rather than keep alternating between the big and small rings. In practice, it only helps a little.
In retrospect it was a bit of a stupid/rash decision to just jump into 53-39 and 11-32 on a hunch or feeling. I got smarter and now did my proper research - by plugging numbers into
https://www.bikecalc.com/speed_at_cadence to see what the actual differences are.
Based on the results, I figure 48-32 is gonna be the sweet spot for me, the 48 being sufficient for top end speed on the fast club rides as well as the easier-paced randonneuring and audax rides. And then as an added bonus I'll have 32-32 for the really nasty hills that our local audax club seems to love throwing at us these days.