I agree with both of those positions. I'm not fast any more, but I'm age-group fast. And it is pretty hard to go fast in winter. Pulling a lot of very cold air into your lungs does damage (not that we've had that situation around here). But my intent is to keep up the slow easy runs in the winter, then add some speed work when things warm up, and presto, get fast, just like that.
And apparently,
short strides are a sort of miracle speed additive.