Alliance are a serie of different mods. On the Star Wars GC, you can play the civil war Empire vs Rebel era + Black Sun and soon the Republic and CIS.
Here you can see some new features as improves in the Republic Starships. The Procurator Heavy Cruiser, The Legacy Star Destroyer and the Protector Star Destroyer receive better weapons which they will increase the difference from these units with another more classic units from the Republic.
Remember, if you like the ground battles at EAW, vote now at this poll Firefoxccmods.com