When you are given a dozen eggs and inspect them closely, you will eventually see they are not of the same size (and sometimes shape) even though they came from the same poultry farm.
If you need a more human example: when you see a set of siblings, you will realize they are different from each other even though they came from the same mother and father.
Same with equity mutual funds and equity UITF, even though they are invested in the same stock market (same parent so to speak), the result of each fund differs from the others. You may compare them one by one... but you can also use just one "ruler" to measure all of them -- the Philippine Stock Exchange Index or PSEi.
Graphs after the jump.