Robert_Charlton - 10:23 pm on Dec 17, 2012 (gmt 0)
With regard to ranking, it really doesn't make much difference which you use.
The main benefit you get by have the keyword in your filepath is that it gets bolded in the serps if you rank on a keyword that's part of the query. If "directory" turns out to be a very long word, you might want to keep it short for reasons you state. I've abbreviated both directory names and filenames. IMO, ranking effects by having the keyword in the path are miniscule.
Having the url truncated in the Google snippet area is a problem only if someone copies and pastes it, not likely to happen, but I suppose possible.