Competition is a sign of a market maturing and I personally can't wait for a little more of it. Competition has moved the 2.0 space forward dramatically already and it will continue to do so in the future. It's important that people have a number of platforms to choose from so that they can work through their decision making process and choose whatever solution is best for their needs.
You should probably also mention the following:
- NXT only supports trading between NXT and assets, not assets with assets. Counterparty supports trading between Bitcoin, assets, and XCP
- Mastercoin requires you to send a small amount of BTC to the founder every time you use its features. They claim this is necessary, but Counterparty doesn't do it.
- Mastercoin will charge 0.3% for trading Bitcoin as well as user-created assets. Counterparty does not.
There are a number of other fields that could be added. This is a simple list that focuses on functionality and forgoes any discussion of model choices (with the exception of "is this project built on Bitcoin"). I'll hand it off to the Counterparty Founders and you guys to do what you want with it. My hope is that it can be added to Counterparty.co/comparison so that it's easy to link to and can be updated as time goes on.