Regarding the questions 'which interview prep is best' or 'which interview prep should I use':
I've heard similar things regarding the common three (Aero, Emerald and Cage).

Those that used service X and were hired said it was the best money they ever spent and highly recommend that service to all future interviewees. The folks that used the same service but were unsuccessful said that they didn't get 'enough' out of it, or that it was not worth the money/effort.

It may be worth doing more than one service to get a couple of reviews of your interview posture/skill/app/resume. If you feel great after one, roll with it. If you aren't sure you're ready, do a second/third service or re-do the one you did first. It's all about going into the interview being comfortable with yourself, and confidence that you are prepared.
Some folks feel confident going in without any prep. You have to decide.