Nxt was created from the new code and was first pure PoS coin.
Blackcoin is a copy of Bitcoin.
Nxt created first multipool for PoS coins. One day later came blackcoin with its multipool
but who cares..
If you can't get free Nxt to try, you can try some free Nxt's clone NFDcoin -
https://bitcointalk.org/index.php?topic=580537.0