Had both on each hand for a 3 day ski trip, and I must admit good old 5 is KOM by far(accuracy HR,battery, comfort,etc..)
pulse oxyometry graph crashes constantly on GC. personally dont nee Spotify or Topomaps(YET), so staying put on 5, happily and patiently waiting for a F6, or 935 successor(hopefullywith OHR OWS). Plus, could not find a decent face for the 5x+. Plus it felt too big a nd "plasticky" on my wrist, IMHO.