I do appreciate strong opinions, I put forward quite a few of my own.

Maybe too many parts of the discussion ran by me here though, as I don't recall ever seeing a Campagnolo-branded rim offered in a 630BSD size.

I have long been a proponent of keeping the 27" route viable, and have even horded singles of some of the lauded and/or rare 27" rims in my efforts to match up and build great wheelsets.

I do find it to be overall cheaper and easier to find the tires I am looking for in the 700c size, such as the racing-team leftovers I sometimes buy by the box full. And so many great tires like Continental "4-Seasons" aren't offered in 27" and never were, so my customers end up selecting a 700c rim size for the wheels I might build for them.

I've noticed an increase in braking leverage using canti brakes when switching to the 4mm smaller hoops, but brake pad-dive also increases unless a wider rim is chosen, which is my preference.

The selection of 27" rims is also scant compared to the vast 700c assortment that is commonly available, especially H+SON TB14 rims which are good, good-looking and reasonably priced.

But with handbuilt wheels taking up a smaller and smaller market share, I'll not dismiss 27" wheel builds since they are a piece of the pie.

I do wish there were race-quality 1-1/8" tires available and I don't mean stiff-rolling tires like Zaffiros, which are a quite-decent tire.

I have some 1" Paselas (I bought a large quantity on closeout) that I have yet to install and try, but looking closely at them the casing looks to be of only modest quality.

With wide rims, I like a tire that measures about 26mm inflated, which most 1-1/8" tires (and 1" Paselas) do.
I am rocking on 27mm (actual, inflated) 27x1-1/4" Armadillo tires this month, which ride smooth at 60psi but which feel quite sluggish to me.