A. The cheaper card has a non-standard cooler. It probably cools better and is quieter but only half the air goes out of the case; the rest is exhausted into the case. It might heat up other components if your case cooling is not adequate.
B. The cheaper card is 1.5" shorter.
C. The cheaper card has a full-size HDMI instead of the more expensive card's mini-HDMI.
D. The cheaper card has a DisplayPort connector.