I'm a forerunner guy as I prefer the sleekness of the FR series vs the epix or fenix series, but that's a personal preference, the guts of the 3 watches are essentially the same for 95% of users it's just the appearance and case that are different.
I will say this about the mips vs AMOLED, I recently updated from the 945 to the 965 and while the watch is amazing for everyday use, I hate the AMOLED for the one thing the watch is intended for….working out. I generally swim and run during lunch, when it's very sunny, and both swimming and running and I can't see the AMOLED screen during the workout. It's terrible. Like I said, love the watch for daily wear and if I workout in the early morning, but in the sun, I wish I had just bought another 945 and called it a day. Just my 2 cents on the AMOLED. The 2 guys I train with have an epix2 and a fenix whatever the current model is and they love them.