Longevity life of the turbo. Will be greater with a water cooled chra.
Pros & Cons:
Pro of the water cooled is longer life
Con of the water cooled is lines / issues with leaks / clutter of the bay / extra money to install
Pro of oil cooled is cleaner bay / less lines / no problems as long as you follow the general rule of thumb about letting the car idle after hard runs.
Con of oil cooled is less life of the turbo vs a water cooled.
Chris.