This article explains the advantages of using the h-index method of ranking over the impact factor, and the virtues of the new Google Scholar Metrics:
The main flaw with the impact factor is that it is basically an arithmetic mean and, consequently, sensitive to outliers. Like a megastar that pulls all the lesser celestial bodies towards itself, one highly influential paper can draw the impact factor closer to its own citation count. This could give a distorted sense of the importance of the journal publishing the paper if its other contributions were largely forgettable. Suppose that in the current calendar year, the journal's one-hit wonder had 200 citations and its remaining 10 articles no citations. This would give the journal an impact factor of 18.2, suggesting, misleadingly, that articles it distributed typically receive 18 citations per year. Contrast this with the journal's h-index of 1, an accuracte reflection of the number of highly-cited articles the journal had published.
Another advantage of Scholar Metrics is its inclusion of web repositories like the Social Science Research Network and arXiv, where authors can make manuscripts or published articles available to the web community at no cost to themselves or their readers. By making it into the top 10 of the h-index ranking, these repositories demonstrate the importance of open access and early views in strengthening a publication's sway.