[Jeeves]

I'm trying to get a bit more familiar with the big 10 AAA corps, and maybe learn more about the AA and under. What books in 4e/5e are the best place for a comparison of each corporation's presence in SR?

How about for a specific setting, like Seattle?

[Mirikon]

In 4E, you have Corporate Guide, which gives a rundown of the Big 10, and the Seattle 2072 book details the major players in Seattle. For 5E, the Market Panic book that'll be coming out soon will be this edition's Corporate Guide.

[Whiskeyjack]

4A core is better than anything currently out for 5th.

[Wakshaani]

In between 4th edition and 5th, you can also get corporate updates in Storm Front, Chrome Flesh, Rigger 5, and some threaded throughout the CFD storyline (Especially via Lockdown!).

Market Panic, which should be out Soon (tm), will be the 5th edition corporate guide, chock full of goodies.