I've been playing Black Shark 2 for a bit now and I'm wondering how EECH (fully modded) compares to it. Has anyone here played both?

I've played the original BS, not the re-edition.
BS has much more detailed flight dynamics modeling, however it relies mainly on loosely scripted missions.
Modded EECH is simpler in terms of controls and physics, but is has more flyable types and each campaign in there is a dynamically changing environment where different units try to destroy each other and capture objectives. You don't even have an alter ego in EECH and can jump into any flyable helicopter at any point in their mission.

Thanks for the reply. If I could ask you one more question, how is the multiplayer community? Still active?

Not an MP guy myself... try asking where the current EECH development happens
http://simhq.com/forum/ubbthreads.php?ubb=postlist&Board=13&page=1