Well I've never read up on HOI 2 but I did purchase AoD a while ago, so I've been reading quite extensively on AoD including Dev Diaries (all), wiki , manual, etc and have only gotten around to play the tutorial so far. It seems like an amazing game, and the Dev Diaries really give me the impression that HOI2 did not offer some of the more promsing/intriguing features of AoD. However that may have changed since the Dev Diaries were months ago. In either case, I would suggest you post in either the HOI2 forum or the AoD forum. But from what I can tell of people's posts in AoD, they consider AoD to be what HOI2 should have been.
EDIT: If you don't have time to read all the Dev Diaries, make sure you check out the last few, where they do the Beta AARs. These ones make an effort to completely showcase the game, and
especially highlight the differences of AoD from HOI2. Also I believe this is a rather common query/debate so a search via google would probably lead you to some valuable threads.
Here are a few links to start you off:
http://forum.paradoxplaza.com/forum/showthread.php?476843-Why-HoI2-over-AoD
http://forum.paradoxplaza.com/forum...ral-questions-concerning-AoD-compared-to-HOI2
EDIT 2: The links above are older, and patches have been out since then, and the latest 1.6B2 is much anticipated, so alot of the concerns about AoD voiced in those threads, and in any earlier threads may actually be irrelevant now. Best to check the AoD and HOI 2 forums for current activity.