Is there a matrix that shows which features are "missing" in the new ECE solutions when comparing it to the previous EIM/WIM solution ?
one thing i know is removal of CMB, you need to use Script editor to configure dialed number prefixes and filters for Agent Request.
A quick look at the routing and workflow guide for eGain version 15 and ECE 11.5 shows that these nodes are missing in workflow options in ECE version:
So I guess that if you need some special functionality, you're forced to go for S+.
There is no official document released for feature comparison, but there is no functional loss in ECE.
ECE is more streamlined and focused on email and chat. Key new features include New and enhanced agent console which is supported on multiple browsers (IE, Chrome, and Firefox). Also, support for latest and greatest UCCE release. ECE also supports SSO this changes the agent experience and also a better experience and better security. Precision routing is another key feature available.
Hope this helps!
For quick and cost effective implementation of Chat with Finesse it might be worth checking CrowConnect solution: