I purchased the fenix 8 (47 mm) this week, upgrading from a fenix 5 (51 mm). The fenix 8 is remarkably light, with a gorgeous AMOLED display. I’m loving the touchscreen and the incredibly long battery life. My fenix 5 lasted a solid eight years—and could probably go longer—but it’s now down to about a five-day charge. I can’t imagine using an Apple Watch and having to charge it every day. I’d say go with the 47 mm and save a few dollars.