I have done alot of research on this aircraft.
And I found this (it is from many comments on different page's etc.)
Level-D :
+ -has a realistic outside
- has a pretty good VC
- normal FMC
- framerate friendly
- - the VC is not so accurate as you (I) expect it to be
- you have only one model; so no expantions
- no weather radar
Captain Sim :
+ - has a good inside and outside
- a very good VC
- normal FMC
- you can buy extentions: cargo, -200, tanker, EWAC.
- has a weather radar (I think it's nothing special, but you have it :p)
- - not framerate friendly; so you need a strong computer!!!
- inside looks a bit as the inside of the B757 of CS (I don't know if you
mind that)
And another option that you didn't mentiond:
CLS :
+ - great outside
- great VC
- you have expantions (same as CS)
- framerate friendly (I think)
- - not a very good FMC
- no weather radar
So my conclution:
-Level-D good if you want sonething thats quite easy and good
-Captain Sim fir those that have a good comeputer and want good quality
-CLS for those that realy love the outside it is fenomenal those details but not a very real experiance
(keep in mind that theres are my oppinions on the research that I have done)