From what I know I believe this is the DPI steps, and yes you can only stick to those then tweak from windows mouse speed settings after.
Spawn:
800, 1800, 3500
Xornet:
500, 1000, 2000
As for the "features", I think Spawn has built in memory to save software macro and button assignments and stuff. Xornet is plug and play so you can't assign different functions to buttons other than their default functions.
And for the color, I will have to test that later. I just know so far my Xornet track perfectly on my Artisan Shiden (White), doesn't own a Spawn so I can't test that one.
Personally I like the dpi steps on the Spawn better but I really don't need any of the other features plus Xornet was on sale for $20 so it was a no brainer for me
![Tongue :P](https://cdn.geekhack.org/Smileys/solosmileys/tongue.gif)
Oh another note, I'm probably gonna go get a CM Storm Recon this weekend. It should also be a viable choice for claw grip user too. I'll let you guys know when I get it ~
Recon:
800, 1600, 3200, 4000