That comparison chart seems to be quite outdated. Unfortunately, I'm not aware of a newer one.
Here's a feature support list, if that helps:
http://learn.extremenetworks.com/rs/extreme/images/EXOS-DS.pdf
The X430 can be considered a "Summit Lite" device. It's a low cost, limited feature switch. Because of this, the X430 uses a separate EXOS image than the rest of the Summit lineup.
The X440 is a bit more powerful and supports a wider range of features. What kind of network implementation are you looking for?
In case you haven't seen it yet, the data sheets and other information for current products can be found on our website:
http://www.extremenetworks.com/products
-Drew