Hi friend
Most likely if you order a PAM 299 N series you will get a O-series because either H maker or Noob have already started the O-series.
That said you are talking about almost the same watches, with the same case, the same base movement, the same bracelet and now, most likely, the same crystal with improved Cyclops. (If you are talking about 299 N-series it would be just worse crystal.)
Therefore it is a taste matter, the GMT function and the GMT markers on dial make the difference !!
Regarding accuracy, we are talking about Super replicas in both watches. You will not find evident flaws in those replicas with solid casebacks.
If you like more simple watches go to 299
If you like complicated dials and GMT function go to 297
Concerning reliability, GMT function is good but you will add more elements to have issues
Just my thoughts
ALE