The DP-10 and DP-8 differ in the following ways.
Rubber plate
The DP-10 has a rubber plate on the bottom of the unit. The rubber plate improves pedal stability and makes it easier to press.
When not in use, it can be stored underneath the unit.
Pedal cord length
The DP-10's pedal cord is 2.2 m long, while the DP-8's is 1.3 m.
Other
The internal specifications of the DP-10 vary depending on the production period, and it is not compatible with certain keyboards when used in combination. See the related Q&A "DP-10: The pedal does not respond despite being connected according to the instructions".