Favorite RPG publisher: I don't have strong feelings either way. I am at a point I identify with the creator's more than the publisher. Having said that, one of the biggest ways a publisher is able to differentiate themselves (the designer being in charge of content) is layout design and graphics direction.
While Paizo and Wizards use many of the same artists, I am more impressed with the art direction of Wizards more than Paizo. I also must say Monte Cook's works are lovely is both art and design. Other books are wonderful with minimal artwork, but pleasing layout. Red and Pleasant Land has both wonderful unique art and beautiful layout and design, while Yoon-Suin the Purple Land is not nearly as well laid out or visually appealing. Primeval Thule is a mixed bag in terms of design. Their choice of background saturation and header fonts confuse me at times.
So long story short. For evaluating designers I look at game content and mechanics, for publishers I look at layout design and graphics. Not that the graphics need be expensive or detailed, just evocative of the setting, theme, or content. So perhaps Paizo is correct in picking art of overloaded characters with fiddly bits everywhere, as that is representative of the complexity, equipment stacking, and bulk of the 3.75 system.