well, i guess you could look at the usability of the websites from a customer's point of view. Visual design, information design, interaction design, architecture of the sites, content.How well do these elements meet customer's needs?How personalized/customized their websites are?
You could also look at the management side of things like, how well do they reply to emails (e.g5 p's = personal, professional, Polite, promotional and prompt!
Hope it helps!
some useful websites on web design:
http://www.useit.com/alertbox/20040830.html
http://www.useit.com/alertbox/designmistakes.html
http://www.useit.com/alertbox/9703b.html