I've used LustyExplorer for one year before switching to CtrlP about 2 or 3 months ago. In my experience:

* speed is comparable * quality of results is better in LustyExplorer * interface design is better, more Vim-like and more consistent in CtrlP * CtrlP doesn't need Ruby * CtrP is more extensible and already integrates a tight pack of useful features (MRU, grep, tags)