Emerald gives a good product for the masses. Video and audio instruction from Aaron Hagan are very informative. Webinars and Seminars are good for practicing fundamentals and building a playbook. Phone top-off product is ok but difficult to practice things like eye contact etc and can lack the energy of an interview. Staff is knowledgeable and plugged into many of the hiring processes.
Cage is highly personalized. You will get many hours of 1v1 prep time and you can schedule your final "top off" with their staff the day before your UAL interview and it will be a "mock" interview...and its across the street from DenTK where they will look at your paperwork, resume etc. You will get less academic preparation materials and you will not have access to "unlimited" webinars like ECIC. Staff is highly wired to the hiring process at UAL due to their history with the company.
I'm unfamiliar with the products from Centerline and Aerocrew but I'm sure they are of similar quality I just don't know their delivery method. Another to consider is FAPA.
Recommend you assess your timeline and learning style. If you have an interview scheduled and have already done some homework in prep for UAL - probably go Cage. If you don't have an interview and are early in the process the ECIC product is good but it takes some time to work through the audio/video lessons.
Aerocrew posted a webinar job fair from UAL. Listen to what Susan White says about the face to face interview. From what she says in that webinar it almost sounds as if people have tried to take "stories" from ECICs videos to the interview and they have heard them all.