I'll leave the specifics of the engines for someone else to explain, but some of the criticism of these models also lies in a few other areas -- and in some cases more noticeable than others.
• First there is the windscreen on the flightdeck. It often doesn't stretch far enough back and the last window frame is somewhat distorted. A check on Anet to see what the real ones look like is the best comparison. Some also feel the nose is not quite accurate as well.
• Then there is the outward splay in the main landing gear. In SOME models this is more noticable than others. For instance the KLM one is pretty good whereas the Emirates one is way out there.
• Then there is the pylons which hold the engines on. From most of the reference I've seen, these also don't match up very well. Surprisingly, the average $35 Hogan plastic model does a much better job (albeit not perfect either, but hey!)
So there you go. Those are my observations in a nutshell. Again, it is best you check photos of current models with Anet photos of the 1:1 (just type the registration into the photo search).
Make no mistake, these models ARE dazzlers with all the surface detail one can possibly take in, and if you can live with these 'niggles', then help yourself to any of Gemini's 777's! I may break down and sucumb to temptation yet myself.