The increased price of a D10 over a D9 or D4 does not represent good value IMO.

The noticable upgrades are;
1. The frame is around 1/2 pound lighter?
2. The chain wheel is 56t rather than 56, and therfore a bigger chain guard is used.
3. The rear brake is V brake rather than Calliper.
5. 10 speed rather than 4ihg or 9 with mech.

I decided to upgrade a D9 instead

See the "upgrading a Mezzo thread" or "Mezzo dualdrive conversion"