Try both and send the samples to Graham and myself
I'm not that familiar with the Lanzones from the Davao area but have tried them on a couple of occasions and i think they are sweeter than the Luzon ones so they may be worth a try. I prefer the taste of Rambutan so id go with them.
Have seen and tasted all the different things they put in lambanog ( coconut wine) to disguise the lovely taste but have never seen Rambutan or Lanzones. Wonder why?
Are the Lanzones about to bear fruit in your area?