Hard to compare the two. I enjoyed and played LB2 more than EECH, though I did play quite a bit of EECH in SP and MP. I admit that I haven't played much EECH since the latest round of updates, so everything below may be out of date
Please jump in and correct me if I am wrong.
LB2 had a steeper learning curve than EECH, though that may be a bit different now with all the EECH improvements.
I thought the LB2 flight model made it EASIER to fly the helos than EECH, but EECH may be more realistic along with the increased difficulty.
The two games are different in conception. While both have DYNAMIC campaigns, LB2 gives you 4 missions to complete per campaign "turn" one of which you will fly and the others which you assign AI flights. Of course you can do them ALL yourself..but that gets tedious.
EECH gives you overall objectives and there are AI flights doing all sorts of things. You can pick a particular flight to lead as is your preference. LB2 is about completing missions, while EECH is more about winning a campaign by occupying enemy territory which all the missions are directly in aid of, including the actual "Occupation" by transport helos dropping troops. Typically an EECH campaign will have a number of missions to
- Wear down defenses
- Destroy enemy forces/installations
- BDA to verify the state of the previous mission
- Occupation of sites by Friendlies
It can be fun to just jump in and fly missions, but if you are really interested in furthering a campaign, you need a more strategic element to your thinking than is required in LB2.
EECH gives a better impression of a big battlefield with lots of units going about their missions. While some of this is going on in LB2 as well, the SCOPE that you see is mostly on a Tactical Level concerned with your missions.
For example, given the schema above, I might notice that a mission to attack an enemy FARP failed, but there is a BDA mission generated to see what the state of the FARP was. I would load out for attack and make sure the FARP was destroyed, and THEN Transmit my BDA instead of just verifying that ANOTHER attack mission should be planned. This way, doing both the ATTACK and BDA, I could trigger the INSERTION mission to take the installation. Sometimes I would then take over THAT flight as well..
If you are interested in Multiplayer, EECH is probably the better bet as the net code in LB2 doesn't support things like hosting from behind a router (which just about everyone has) without using some Virtual network app (Hamachi, TUNNGLE etc..). SUCH A SHAME!!!