I think you need to compare "Esper Enterprise Edition + EsperHA" with Coral8 to take into account the GUI + high availbility options. EsperTech's core product is open source (Esper / GPL licensed), while Coral8 is not, which can also lead to different pricing ranges and strategies.
I think that Coral8 CQL and Esper EPL are roughly equivalent as well as extensible. These two products have all the software, documents and samples available on the Internet. Esper has published performance tests with code to run them, albeit for fairly simple scenarios. The best way to compare performance is to prove the concept with the two vendors that I assume.
It seems that the two companies get reasonable trends in various industries for both direct customers and OEMs with independent third-party suppliers from their advertised customer links.
http://www.coral8.com | http://www.espertech.com
Alex
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