I think part of the problem here is this idea of "best". There is no one best FE, or there would only be one FE. Different FE's lend themselves to different applications, different configuration approaches. Take GameLauncher and Lazarus (sorry, I haven't used DK yet) as examples. GameLauncher allows you to customize the display and command line of every individual file in the list and is cross-platform, but has no way of organizing files beyond the list you provide it. It cannot be configured from the interface (this is a feature to some, a problem for others). Lazarus lets you configure some things from the interface and has a powerful filter function, flexible skins and multimedia support, but it's dependent on external players like MediaPlayer and RealPlayer, runs only on Windows, and can be tricky to deal with if you're not a big user of the assorment of ROM utilities. Neither of these is necessarily better than the other, but they represent widely differing approaches to configuring and presentation.
So a roundup that summarizes features and points out strengths and weaknesses is a good thing, but trying to decide which is "best" is impossible.
--Chris