Obviously, PoS started with Peercoin. There was a reason I ended the sentence with "as it's accepted today". You should and I know that Peercoin's PoS is inferior to NXT's PoS implementation.
Inferior in which area? As I know Peercoin has less theoretical PoS security problems because it's using PoS and PoW simultaneously.
AFAIK Peercoin uses centralized checkpoints and opens up the possibility of stake grinding. But I'm not 100% certain.
In the end DPoS is probably one of the best PoS integrations, as it scales wonderful and allows the blocktime to be very fast/constant. I dislike DPOS because of the necessity for people to vote on delegates. Now this may work perfectly fine in such an enclosed envirement that we're in right now where the userbase is very small but I doubt it'll work very well if any DPOS ever hit's mainstream. No normal user wants to be bothered with stuff like that. They want stuff to just work so the majority of users prob wont vote which kinda defeats the point of the excercise. As always - maybe I'm missing something