I think people dont pay too much attention on the quality of texts and videos of HDTV advertisements, as long as the texts are readable from where they are standing at any given time of the day/night - which is usually far enough.
Just get the biggest one in your budget whether it be LCD or Plasma. In the past Tokyo had mostly Plasmas for advertisements because there were no big LCDs/LEDs and the price of big Plasma is cheaper. Nowadays, you can definitely get big LCDs as well, however, I dont know exactly your available HDTV options and price ranges in Manila. If you're going to place the advertisement in a very bright area, you might as well select an LCD/LED - indoors, both should be OK.
