But Will, if you're taking that argument, you've left out half of it. Yes, we wouldn't have a winter to warm up after, but we wouldn't have a summer to cool off from either!
In the Eternal Equinox scenario I envision, it will still be cold at the poles. Not deep, polar winter as we know it now, but pretty cold, subfreezing temperatures. I also believe that what we now think of as the tropical zone (roughly 23N to 23S latitude) would remain very much the same. So, someone living in Ecuador will notice no change at all.
Where I live, about 40N, is 5 degrees latitude south of the halfway point between the North Pole and the equator. And, it makes sense that where I live would, in Eternal Equinox, feature weather you'd expect halfway between Arctic and tropical.
We would still have jet streams, and I don't expect that they would be more tame and predictable than they are in the real world now. Therefore, in Eternal Equinox, my region might still be subject to dips in the jet that would bring cold air over us for a period. And, we must also allow for "ridges" in the jet that could put us on the warm side as well. Weather wouldn't be exactly the same, day after day. There would be variation. But seasons as we know them would be gone. Warmer and colder than usual temperatures could happen anytime, rather than being tied to the calendar as most such occurrences are now.
Your "Vila do Corvo" argument is apples to oranges. Maritime climates would still exist. The Gulf Stream would still exist. And so, I would expect, temperatures would - much as today - not follow a strict correlation with latitude. Big water would still be big water.
Of course, neither you nor I can have our theories proven, short of the Earth actually aligning itself as I've described. So, it's simply my conclusions vs. yours with no actual winner.