I can try.
First of all, Ethereum is not a coin. It’s a p2p application platform, ie. something to run those “dapps” on. In ethereum system “ether” token serves as fuel for execution of smart contracts. Basically you burn ether to run smart contracts. That is anti spam feature in it’s essence.
If and when they implement PoS - ether tokens will become sort of a “stake” and could be used to issue new blocks.
Now Peercoin is a coin, like Bitcoin or Litecoin. It’s primary purpose is to be a form of decentralized money which can be exchanged for goods and services or it can be used as decentralized store of value (digital gold). Unlike with Bitcoin, “peercoin” tokens are not simply coins used for transactions but also a stake in the Peercoin network - allowing you to issue new blocks.
Unlike Ethereum, Peercoin cares a lot about decentralization and censorship resistance. This is a must due to different use case. Peercoin blocks are issued every 10 minutes, while Ethereum blocks are issued every 12 seconds and this fact tells us a lot.
Ethereum needs fast blocks because it is application platform and it has to be fast, while Peercoin takes some time between the blocks to allow everyone on the network to synchronize and try to make new block or simply validate a block made by someone else. As result only people who own powerful computers with fast internet connection can run a Ethereum node while just about anyone on the planet can run a Peercoin node.
There is difference in proof-of-stake algorithm too, Peercoin’s PoS algo is made to be fair and give equal chances to everyone on the network. Ethereum takes more game theory focused approached with their complex behemoth PoS algo which will be gamed and exploited leading to centralization. Not a bad thing for Ethereum, they have different focus as I have stated above. They need something performant and they cant have blockchain reorganization.