What is the Difference Between the WE7281 and the WE7282 4-Ch 100 kS/s D/A Modules?

The output connectors are different. The WE7281 has a clamp type terminal, and the WE7282 has a BNC terminal. Also, the maximum common mode voltage, and maximum voltage between channels etc. vary in their specifications between the two instruments (the WE7282 is lower). Please see the specification sheet for more details.