PPCoin augments "proof of work" with "proof of stake" to secure the network which is much more efficient. So, all things being equal, transaction fees with PPCoin should be lower than Bitcoin. And I believe transaction confirmation times are half that as Bitcoin?
Freicoin has a 5%/year demurrage rate that goes to miners forever. So, this may encourage a more secure network, and lower transaction fees. The demurrage could also help increase monetary velocity.
I believe the only thing different with Litecoin is the hashing algorithm and faster confirmation times?
PPCoin - I have tried to read and understand this. However, so far, I don't understand why this is better. I thought they wanted mining to be hard to do.
Freicoin - Burning money during each transaction kinda sounds like what they did in world of warcraft. Not sure why you would want to do that
Like I said, they don't really offer anything New. They just offer to do the same things differently.