Going with anything not brand name implies risk. There's a reason cheap knockoffs don't have warranties. Burris is reputed to be great value, warranty, and performance. The cheapest dot sights that function are meant for use at a range, occasionally. Repeated long-term use subject to bumps, temperature changes, humidity, even submersion and occasional dropping, you want quality. And you know it's quality if there's a warranty.
As well, higher quality optics are more forgiving with parallax,
http://www.bullseyepistol.com/dotsight.htm and the mounting attaching the optic has to be rock-solid and not loosen up.
Of course, you get what you pay for but there's diminishing returns when you get to the very top of the line.