hey BlackReaper, welcome to the One-Ring. I must say myself I've always been fascinated by Moria, and there is some truly great terrain there if your into making your own terrain. In army wise, I agree it's not the best - but if your looking to expand from the MOM box there's the new 'Cave Drake' and several other great pieces. I have the Mines box too, and I used it for some time. It's good to see you've experienced some other role playing games before, if I remember battletech was mostly robot/machine things?
Isengard has it's advantages, and probably have more range to chose from. As Spud said you will have a smaller army because they are more powerful, which in my opinion find better.. so I can control all my troops without getting overwhelmed. I agree thought that you could mix & match a bit.. look forward to seeing what you do.
Drum