browsing this forum for bali but thought i'd chime in :)
i grew up in palawan and make it a point to visit at least every couple of years to see family and i would like to say that palawan is worth it if you're already traveling to Manila and don't want to go to boracay OR if you want something different from thailand.
i just came from thailand in january and we were in the khao lak area. we decided to go there because of all the reviews saying phuket was super crowded and that phi phi was better to get to if coming from krabi. anyways, khao lak was just like any other beach town though i liked it because it wasn't too crowded. we went on a day trip to the similan islands (1.45mins in a bumpy speedboat) and while some islands on that trip were super nice, you are still in that speedboat with like 30+ other people. when we got to the most popular island (donald duck island), there were probably 100+ other tourists with you on the beach. it wasn't until we went to a different island for lunch did we actually get some "alone" time. or i guess you can hire your private speedboat so you can go wherever you want but that can get costly.
so one of the biggest differences between thailand and palawan (or other islands in the philippines) is that you can still find secluded beaches in the philippines and still take small boats. if you want seclusion, you'd be able to get it in palawan. i mean, my friends and i went to coron one year and we had one entire island to ourselves. the 6 of us, 2 boat men of our privately hired banca, the caretaker of the island and his two dogs. granted the accomodation was basic at best (no hot water and air conditioning); but we had one of the best times of our lives in that tiny speck in the ocean.
in the end, i think you are looking mostly for a place where you can use your miles for airfare and points for hotel accomodation and i can say you won't be able to utilize both in palawan.