My Y-series Pixelbook with passive cooling performs as well as a U-series laptop from the same generation -- until I start a sustained load. At that point, the U series systems pull ahead. Actively cooled Y-series systems get pretty close in lots of applications only falling short due to half the cache.

If you are doing lightweight stuff where the cores don't really need to spin up, then they'll probably be about the same. Otherwise, you'll be stuck at a much lower base clock.