I'm from Philippines
Galaxy S or Galaxy SL (in Philippines Samsung Store refers to it as Galaxy S-LCD version).
Galaxy Ace is around 14k in peso, while SL is 18k. Advantages of SL is that it has a higher resolution screen and 1ghz CPU and a dedicated GPU. A Galaxy Ace only has an 800Mhz CPU and no GPU, so its gaming capabilities is not up to par with an iPhone. It has a 4inch SLCD screen as well, superb and very nice compared to regular LCD that Galaxy Ace uses.
Galaxy S on the other hand costs 25k pesos, and looks exactly like a Galaxy SL, except that it has a better graphics chip and an AMOLED screen, so better display and better gaming capabilities as well.
All three mentioned has a 5mp camera but no flash.