For one thing, OZ allows you to choose how you want your memory allocated, instead of a mandatory 32-32. I quite like Opie, as well. As for SDL support, there are Opie SDL libraries available in the
feed, and SDL support is, from what I've gathered, quite good. Doom runs perfectly fine for me, with no lags, and SNES games run reasonably well with the sound turned off. The 2.6 kernel is being ported currently. For me at least, it's rather difficult to explain why I prefer OZ, but the last time I tried to revert back to the Sharp rom, I switched back soon. I recommend backing everything up and trying it out. Be sure to pick Opie, (unless you don't mind not being able to use Exult, or any other Z software), and memory-wise, I have 48-16. You can always revert back if you don't like it.