I had the original Apple Watch and upgraded to the Series 3 with LTE a year ago. The Series 4 looks amazing with it’s larger screen, but the speed is the real winner.
Did I mention the Series 4 is fast? Series 3 was pretty fast. Series 4 is fast in a way that you never think about it; things just work, fast.
if you haven’t had a smart watch before it might seem odd that you need so much speed for one, but any delay at all is a big usability challenge for a smart watch. I’m trying to hold off and skip the Series 4, but it’s tempting given how good this new Apple Watch seems to do.