In order to reduce weight from close to MTOW (Maximum Take Off Weight) I would taxi to the longer runway cause it is far away and use Flex Take Off (It's de-rated thrust but called like this in Airbusses) if needed otherwise to reduce a bit more weight TOGA (Take off - go around power) which puts maximum take off thrust available.
If the RWY is let's say 3300 meters and I am close to full weight with the Airbus A320 I would choose TOGA if bad conditions such as rain, etc.. or Flex Detent in good conditions. Longer RWY's are better as you most of the time do not need to brake maximum or close to maximum in order to stop incase of an aborted take off. Actually it's more "recommended" to use the RWY that is said in the flight plan paper.
Taking off with MTOW almost always causes structural damage.