The 0404 probably has better unprocessed sound, since it seems to have better electronics on board. However I'd say they are pretty close. Regardless, I imagine the 0404 is technicly superior. The X-Fi will offer you the ability to process your sound, which many people like. The X-Fi's HRTF is second to none.
My guess is it would probably not do much for you to get an 0404. You'd probably have to get at least a 1212 to notice much difference, and that's assuming that unprocessed sound is your thing.
Do remember that Emu and Creative are one in the same, there's a lot in their designs and IC usage that's similar across their cards. The Emu cards are designed for pros, the Creative cards for consumers, but it's the same team working on both.
What I would do first is figure out if you like the X-Fi's sound processing. Try listening to it in headphone mode and two speaker mode with CMMS on and off. Of those four, pick the sound you like the best. If it's 2 speaker mode, CMMS off, well that's pretty much unprocessed sound, in that case, you may want to look at an EMU card. If it's any of the others, then you like the processing the X-Fi does and should probably stick with that.