I like the texture of the mouse (slightly rough), the shape, and that it looks like a proper mouse with only 4 buttons not 20 like some have now. It doesn't look like they evolved it with the G9, that looks stupid.
I use USB as it seems more responsive with less lag than wireless, but I haven't tried wireless mice for ten years. I'd consider wireless if they're heaps better these days.
Is there a Logitech laser mouse that's textured which has a limited number of buttons?