The Stellar Account Viewer is definitely good enough for accessing your assets on the network. There are some differences however.
For instance Stroopy.org gives users the ability to view their assets without having to provide their secret key. Your secret key is only required for actions that require signing a transaction. Also Stroopy.org is built with both desktop users and mobile users in mind (as you can see from the image above) whereas the Stellar Account Viewer was built more with a desktop user in mind.
Stroopy.org works on any browser, even old browsers that do not support ES6. This is important to be able to reach people that sometimes still rely on old devices, especially in less fortunate countries.
This is just the beginning, more features are on the way.