A casual evaluation will impress many people with the Galaxy watch line. It looks great, is mechanically solid, and my version (the original) has great battery life). However, all one needs to do is read the many thousands of dissatisfied users to see that its features engineered and supported at the level of novelties and not the level of precision functions that characterize Apple's watches. A look at reviews about the watch's ability to track exercise (heart rate in particular) and sleep (deep sleep in particular) will make the point clear. My current Galaxy tracks sleep and exercise perfectly -- about 70% of the time, meaning that the watch is all but useless for someone who wants or needs to count on it. Among the problems are the watch's inability to keep up with rapid heart rates (>135 BPM) when exercising vigoerously; it simply stops counting and there is nothing to can do about it. On other occasions, it counts each beat twice. I have stopped to verify several times.
This Tom's review should also point out the the new Galaxy 3 appears to be a generation behind the Apple 6 features that will soon be released. SpO2 measurement comes to mind as one major difference.
I regret that I'm otherwise locked into Android systems because the Apple watch is vastly superior. The medical community has adopted it because its features work every time and can be integrated with a growing list of technology interfaces. It is revolutionizing tele-medicine. No one is looking to Samsung for this.