The KA tell's you that you are buying the DC720 in a kit. DC720B tells you are buying the DC720 as a bare tool.
The DW929 is roughly a 10yr old model. It only had a 3/8" chuck. The DC720 has a 1/2" chuck enabling you to do larger tasks. In all honesty, the two drills are nothing alike other than the color and name. The DC720 has a frameless motor, while the DW929 used the older CAN style motor. The DW720 is my favorite compact drill on the market. If you have not read my comparrison on it.
Check it out here.