directory metrics

how can i evaluate different directories?

[kane2222]

when a media buyer or site owner evaluates the plethora of directories and advertising/submission options, what metrics should he/she be looking at for comparison purposes?

what metrics are available to compare one directory with another? i compiled a short list below, but i'm sure i'm missing some elements....

- unique visitors per/month (audited)
- search queries per month
- google page rank

i don't think i'd use any of these:
- hits/page views
- length of stay

anything else i should consider?

[windharp]

Distribution to other directories / search engines maybe?
(Is a copy used by someone else? Are SEs spidering it properly?)