Zowie EC1 Evo vs EC1-A?

Solution
the sensor on the ec1-a is slightly higher dpi at 3200, on the ec1 evo its 2300.
other than that there pretty much identical in shape, size and weight.
Features and Specification:

Ergonomic right-handed design
Plug and play - no driver needed
Perfect lift-off distance: Only 1.5 ~ 1.8 mm
24-step scroll wheel
DPI ( Dots Per Inch ): 400 / 800 / 1600 / 3200
Adjustable USB report rate 125 / 500 / 1000 Hz
Connector: USB
Buttons: 5
Length of cable: 2m / 6.6 ft
Operating system: Win2000/XP/VISTA/7/8
Mac OS X v10.2 after

http://www.zowiegear.com/index.php?i=news&p=62 EC1-A and EC2-A