Are you talking about EnCoders? If so I would say one of the biggest is EnCoderPro. They all work on the same concept and navigate the same. The verbiage may be a little different but if you can handle one then you can do them all. If you try a few out you will find one that you like the most.
I am a fan of Find A Code because it is easy to teach with when I want to copy a code and description and paste it into an e-mail. Laureen has used that one, SuperCoder, EnCoder and a few others. She has things she likes about each. The AAPC is now marketing their new one. I used it during the trial period and it was real nice. I suspect as time goes by they will become one of the top if it is cost effective for them.
However, I keep my manuals close at hand all the time because if I am ever in doubt I know right where the information is I want to find. They are my good friends...