http://riecoin.org/: ..
In Primecoin there is no practical way of estimating the time before finding a block, moreover difficulty 10.1 is easier than 9.9 making
it impossible to estimate how secure the network is.A centralized checkpoint system is implemented inside Primecoin. While it is disabled by default, if FUD about attacks start to spread, I believe some people will panic and enable it.
A centralized checkpoint allows its controllers to perform double spends without any need for any % of hash rate. Can we be sure it will not be hacked and/or abused?
Riecoin is capped to a fixed amount of coins (84M), but Primecoin has no limit. While it is arguable, we believe our deflationary model - similar to Bitcoin's - is better.
1min block speed would bloat the blockchain and create more orphans, stales. We have 2.5min which was tested for years in LTC. I don't know of any 1min coin that has years of testing. I think it's not true that 1min is fast enough for waiting in a line when you buy a coffee: with blocks targeted each minute, you have a 1 in 150 chance of having to wait more than 5 minutes for a block, this would still be unacceptable for some coffee stores. Also, with 2.5 each block requires more work, meaning we will have larger prime numbers sooner.
A couple of questions:
Since Primecoin is able to keep the block times at ~1 minute, clearly empirical estimations work (though with a delay of a few minutes, but that doesn't matter, does it?) for determining how secure the network is, and how long the block time will be, no?
If the block time were 1 minute, wouldn't the same amount of work be done in 2.5 minutes, just with the potential of 2.5 blocks being found instead of one? Doesn't the amount of work being done strictly depend on the hashrate, not the difficulty? I.e., maybe the solutions accepted for 3/5 blocks are simpler than would be accepted for the 2.5min case, but shouldn't the other 2 solutions should be just as difficult as if the block time were 2.5x more (on average)? I have no experience making a miner or looking miner code, so I am just guessing based on how I think miners work. Anyway if this is true, Primecoin would win for this point since it's hashrate is surely higher than Riecoin's.
Thanks for your answers!
Edit:
Also, Gatra claims Riecoin can find large primes, but in the verification section of the whitepaper for Primecoin (
http://primecoin.org/static/primecoin-paper.pdf), Sunny King claims Primecoin can't find large numbers because it would be hard to verify the Proof-of-work. It doesn't go into any detail. Is he wrong, is there a reason this won't apply to Riecoin, or will this eventually become a problem?