The Xornet. No question.
That said, I imagine it'd be a bit short for you unless you switch to a fingertip grip. At that price range you're really not in the market for anything that could be described as "decent". The sole exception might be this, which has a sensor as good as any mouse out there, but you're sacrificing the existence of side-buttons.
Can't you get a paper round or something?
They probably are the same. It's not unusual for lower-end companies to use the same OEM and just slap their own branding on it. Hell, even the higher-end companies do it from time to time.
DPI doesn't signify the quality of a mouse. If you're running 4500dpi on a 1080p screen with EPP off and 6/11 pointer speed, you'd probably be better off lowering it (edit: Just saw your sig. At proper settings, 4500dpi will be detrimental to your performance).
Until you get to 4k or multi-monitor setups, 2k should be enough for anybody (and considering he can't afford more than $25 on a mouse, I'm guessing 4k/multi-monitor is unlikely).