It is difficult to compare EzDrummer and GA4 as they are not 100% similar software. GA4 is much more a loop player and EzDrummer is a versatile drummer software, although GA has taken a huge step towards being a drummer software from GA3.
The pre-programable PADs in GA4 with pre defined loops that can be changed live in complexity is not in EzDrummer. The MIDI loop builder in EZ Drummer is perhaps a little similar to GA PADs, but GA 4 has, with key triggering and complexity slider, much more variety. On the other side is EzDrummer much more friendly when it comes to monitoring and browsing MIDI file. The file system in EZ drummer (or Superior Drummer) is far far far better than the cumbersome media bay/browser of GA4.
When it comes to sound I like the sound of the Rock Kit and the Vintage Kit in GA4, I still find the sounds in Toontracks Ez and Superior better, especially after the right compression and reverb.
I have a couple of questions on GA4 that I will address in another topic.