We look at these questions, knowing that they have no universal answer. Which is better a Corvette or a Mustang, Coach or Prada, Emeril or Rachel Ray, Tag Heuer or Rolex?
There are people who can wear both contact lenses equally well, and both have similar durability profiles. There are people who can wear the PureVision lens and not tolerate the O2 Optix, and vise-versa. The manufacturer's representative would be happy to have one of their representatives pitch the case in favor of their lens. Afterward, you and everybody else could still not answer your question.
The O2 Optix lens is slightly less expensive than the PureVision lens. The PureVision lens transmits oxygen more easily to the eye than the O2 Optix. Whether these are significant factors for you and your wearing of contact lenses are all part of the discussion between you and your eye doctor.