Hi, Thanks for the question, this is the first time we have been asked about Kapow. From a brief look at the capabilities, a big difference is going to be how each product integrates into your system architecture. It also doesn't look like they have an out-of-the-box front end solution, so you'd have to find a 3rd party front-end or develop your own.
Kapow looks to be stand-alone whereas ME is integrated into SharePoint. Management for ME confituration is all done from the SP web sites, Kapow probably has a management console that is seperate. ME allow users to browse their SharePoint content using the same URLs they do from the desktop.
ME is very SharePoint-centric. You can install, deploy, configure and browse to your mobile sharepoint sites in as little as 30 minutes. Beyond that, ME provides BI capabilities leveraging Excel and Excel Services. And because of its API, ME can be extended to surface data from any system and be customized to look however you want.
I would encourage you to trial both solutions, and would be curious to know your thoughts on both. You can download a trial for ME from
www.mobileentree.com/download-joe