The smartwatch market has long since ceased to be a race to see who has the biggest screen or the most sensors. Now the battle is on more subtle grounds: who understands you best, who monitors your health most effectively, and, especially, who lets you sleep with your watch on. This time I've tested the Apple Watch Series 11, the Samsung Galaxy Watch 8, the Oppo Watch X2, and the Withings ScanWatch 2, four offerings that represent two very different philosophies about what a watch should do in the 21st century.