There are major PCB differences as well. The Ex doesn't have the internal pin headers like most Creative cards, it has a multi-function bracket on the rear plate that runs to the external breakout box. It also supports ASIO 2, which neither the Platinum nor Audigy 2 standard support. The software package is also more robust with the Ex. Unless you are a prosumer, musician, or serious audiophile that uses your computer for sound editing/sampling/recording etc., you probably won't notice the difference.
Chiz