Have both. Prefer Naos because it is quieter (clicking and scrolling wheel), and seems wider, which gives me more room for my entire hand. Naos software is also better than Ikari's; can make more adjustments. Naos also has weights. Also, Ikari's rear profile is very low, which sometime causes me to pinch my palm underneath the mouse (if my thumb is too low, or on the mat during casual use). But, perhaps you should go to a store and see if you can try them out - You may see/hear/feel things differently. Ikari does come with better skates, but these can be cheaply replaced on the Naos (if you're not satisfied with the originals). Also, Naos is a pain with Linux - Have to remove and replace USB after a shutdown or reboot into Windows (if you're dual booting). Mionix knows about this, but has yet to do anything about it. Steelseries seems better with fixing/updating software and firmware issues.
Hope I've been of some help... Good luck.
Just relized that I didn't mention that I have the laser editions of both mice. If you are considering the optical versions of these mice, the above comments, except for the Naos wieghts, should still apply, since the bodies are identical.
Edited by therecorder - 4/18/12 at 12:30pm