Universal adoration for
Net-a-Porter here, but I find it hard to accept anything less from a store this high-end with sale policies that stubborn. I sort of take the site's chic styling for granted too, because unlike Neiman Marcus, Saks, or Barneys, Net-a-Porter doesn't have a physical outlet, and presentation is the only way through which it can move merchandise.
For sites that use mannequins instead of models, I like
Cusp better than Bluefly and Barneys.
A very underrated site is
Endless, which specializes in shoes and has expanded to bags. From the size and clarity of the images to the multiplicities of the camera angles, this one is truly hard to beat. Zappos and Amazon can't compete. The newsletters are also surprisingly and amazingly well-edited. Their specials on caged heels, patent oxfords, and ankle boots were better than most magazines'!
As far as medium-priced shopping mecca goes, I regularly visit
Shopbop and
Revolve Clothing but don't think either use models that do their merchandise justice. I am not especially fond of Revolve's models and I don't think I like any of Shopbop's models

now that their Asian girl has briefly moved to Revolve and now appears on a smaller site. Shopbop's site is very well designed though, and the search function is smart--gotta give them credit where it's due.
In terms of photography, I definitely prefer
Basic Boutique and
Couture Candy to both Shopbop and Revolve. Couture Candy has the best pictures of jeans I have seen. Below is a comparison:
Basic Boutique vs Shopbop vs Revolve:
Basic Boutique vs Shopbop:
Basic Boutique vs Shopbop vs Revolve:
To me, Basic Boutique has the best pictures. Things just look so much airier there. Shopbop's and Revolve's models are trying too hard.
picture source: BasicBoutique.com, Shopbop.com, RevolveClothing.com