Effectively Legendary Treasures is reprinted artwork for many past BW cards, so if you want to collect the reprints (and large quantity of EXs) then you could go with that. FF will likely be the most expensive set out of those three in the future due to featuring 4 Charizards, so if you plan on ever selling, try completing FF. PRC is just a nice set overall, with heaps of cards. PRC is the largest of the three, while FF is the smallest.