The WAP site has a much more simple interface that works on all other devices where there is no native app available.
The features are practically the same, except it doesn't have push notifications, charts, twitter feed, fractional quotes support, the shortcut to reverse positions, and the possibility of setting a default order settings per contract. Also in the apps, you see the quotes auto-refreshing, and in WAP you have to Refresh in order to see the changes.
All the rest you can do: place orders, edit them, cancel them, close positions, close all positions, see order details, browse and search for contracts, add them to your watchlist, set email notifications for fills and price alerts, see you balance...
For Gain Capital / Fully integrated with OEC Trader:
You can log in with your existing credentials or create a Free Demo Account with simulated funds and explore all the features before trading real money.