PIVX is better in my opinion.

Key differences between PIVX and DASH:

100% Proof of Stake – PIVX supports an advanced version of Proof of Stake (POS). This is a system that relies on master-nodes to verify transactions instead of miners. PIVX is 100% Proof of Stake whilst DASH is only 50%. This means DASH still relies on miners whilst PIVX does not.

Seesaw reward mechanism – PIVX uses an advanced mechanism to distribute block rewards. 90% of the reward is distributed to the masternodes and stake nodes, whilst 10% is distributed to community projects.

Availability – PIVX is a newer currency than DASH and less availability. It is traded on less trading platforms.

PIVX solves a lot of problems that DASH has and it is much cheaper. It will be interesting to see how it plays out.