Should you submitt 60 diffrent articles to 100 sites or 1 unique = 600 article to 600 sites ?? saying that all directory site were of equal page rank.
You can submit 60 Article To 600 Article Directory that case it's also not harm becouse article directory are like that you are allowed to submit one article to multiply directory. But it;s always good if you submit unique article to each directy that case 600 directory to 600 article directory
If you have enough funds to get 600 well written articles then by all means it would be better than submitting 60 same articles to 100 directories. But if you do not have that much money then by submitting the same 60 articles to hundred directories will be ok as well.
I will do both partially. Writing cost for 600 unique articles is too high. Spinning doesn't produce great results anyway.