I am upgrading from my series 6 AW and am torn of which watch to go with. The reason I originally upgrades from my previous series 4 to 6 was the blood oxygen sensor. As someone who has been prone to get bronchitis in the past the idea of having an idea of what my blood oxygen levels were was a nice option to have. Now with the B/O sensor being removed I have to decide between a base series 9 AW (GPS) w/ the B/O sensor that's still available or my dream AW, a graphite SS series 9 w/out the B/O sensor. I've heard a number of people say that the B/O sensor in the series 9 wasn't reliable anyway so should that be a sticking point? Is the B/O sensor something you use? I was able to get both at a great price so I'm stuck on which to go with.... series 9 GPS w/ B/O sensor or Graphite SS series 9 w/out B/O sensor...