I just read that sentence, and it doesn't explain anything. It just says they're not what he likes, so here's another one that might work: http://www.mucommander.com/
The separator of TotalFinder and Xtrafinder is just too thin. I want to see right away which side is in focus. When you click on one of the two windows the other one becomes washed and is also covered by the shadow of the active one.
For me, that's better usability.