Both settings have way too many books (i.e. >1).
The idea of selling 4000 page books doesn't appeal to suppliers or consumers. There are multiple books for a setting in case you don't want to incorporate certain aspects of the setting in your version. If your entire Eberron campaign is based in Sharn; it might be a good idea to buy
Sharn: City of Towers. Don't want to focus on the more experimental magics in the plane? Don't buy
Magic of Eberron.
(and special guides just for players)
Player's Guide to Eberron. The regular campaign book slimmed to just what a player needs, plus more material focusing on them instead of the setting.
How is it better?
It uses magic in a very unique way unlike other settings. It's more common, but less prevalent. Almost a magepunk setting. Technology is implemented through mainly magic and elementals instead of electricity or combustion.
The setting makes level progression sane as you are compared to your encounters. High-level in Eberron is pretty much Lv6 and up. Lv12 and you're truly epic and can reliably challenge leaders of entire city-states. This is kept in check by there being an entire bureaucratic system across the land. Laws matter, and Mister Chaotic Stupid will likely get his character jailed on the first session instead of being smitten by the DM in the sky.
