Spa Wayfarer - 38mm
Pub bike and CX/gravel bike - 35mm, both set up for roads mainly.
Singlespeed and Road Bike - 25mm
although I've hardly ridden recently as life/family have got in the way.
I prefer the wider tyres at a lower pressure as although they don't feel as fast, because they are smoother, in general the speed (or lack of) is about the same and they are more comfortable. The two bikes with 25s are caliper brakes and 28s are a struggle to fit, especially on the singlespeed with guards.
As well as changing road surfaces and gravel cycling's current enthusiasm, I think there's something to be said for changing geometries and frame properties between the 1980s and now. Bikes are much stiffer than they used to be, especially around the head tube, fork and steerer. I used to have an old 501 road bike from the mid-80s, and that felt relatively smooth even on 23s. The bike had a 1 inch threaded steerer, 26mm bar diameter and quite a relaxed geometry. If you put some work into that bike you could feel the frame flexing.
Compare to my other road bike (a 2014 CF Merida Scultura, which is supposed to be a slightly more endurance focussed bike), which has a beefy head tube (I think it's 1 1/8" - 1 1/4", buit the taper may even be bigger), and a much steeper set of angles. That bike on 25mms feels much harsher, but it also feels more responsive because of the stiffness in the frame. I wonder if some of the migration to larger tyres and lower pressures is to mitigate the other trends towards stiffer less compliant bikes?