PoS verses PoS3 (Blackcoin)
This removes coin age and moves to number of confirmations, as to whether it is more or less secure than the original ,
currently unknown, it seems more secure, however without coin age it may make the coin more susceptible to a 51% attack where someone tries to purchase the coins outright, because it kind of removes the Chaos factor that protect the original PoS.
(Chaos Factor: Even thru you know how many coins there are, you don't know their weight or when they will be staking.)
Main Issue for the Blackcoin design is purely economic ,
1. interest rate is too low , at 1% per year it is a crappy investment
2. Minimum Time before staking is too short which allows the rich to monopolize the Staking Process and actually crowd out poorer investors delaying their stakes.
PoS verse PoSP (Crypto Bullion)
Both still use coin age , so security should basically be the same.
After looking at their Whitepaper.
http://cryptobullion.io/white-paper/It has a similar issue with allowing staking to start too soon (1 hour)
which allows the rich to monopolize the Staking Process and actually crowd out poorer investors delaying their stakes.
Also there is an underlying incentive to DDOS other PoSP users so that your own staking will receive a higher % of the staking.
PoS Specs do matter , longer minimum stake times are required to keep the wealthy from monopolizing the Staking Process
Which the current PoS3 & PoSP ignore, which will decrease their adoption rate by the majority of less wealthy users and hurt them in the long run.
(In one economic regard, they function like PoW, only the wealthy will see the most profit.)
(However if they increased their minimum stake age to 15 days or more , they could remove that issue.)
(They could also increase their interest rate to 5% per year and be a decent competition to Utility Stocks.)
FYI:
You forgot PoS II from MagiCoin & NobleCoin
They have a declining reward if you don't stake within 2 weeks or so .
Where if you have the wallet offline for more than 4 weeks, you have to send all of your coins back to yourself to reset their age , so you receive a higher stake.
Oddly enough , it was designed to make sure more people staked, but with only a few hours needed before staking ,it also favors the wealthy holders, but makes them stay online more so they don't lose stake rewards.
FYI2:
Of the 4 coins mentioned above , the top choice if you want to actually earn, is Noblecoin with a 8% per year interest rate.
You just need to stake every 2 or 3 days and keep between 1½ million to 2 million Noble per block to stake effectively.
Noble also has a nice difficulty #s , so it is secure from the history attack worries.
https://chainz.cryptoid.info/nobl/
