Priceline definitely has a better color scheme. The contrasting colors that they use help the eye pick out the important parts on the page. It is also pleasant to look at. On the other hand, Expedia's site doesn't use much color. Therefore, there isn't much contrast; attention isn't drawn anywhere except colorful advertisements that scatter the page.

Priceline's site is also easier to read. Since the font sizes vary and are (for the most part) fairly big, the user does not have to strain their eyes to read. However, Expedia's site has smaller font with too much text. Also, since Expedia's page is crammed with items, it is difficult to pick out the parts that are necessary/needed for usability.

Priceline and Expedia both do a decent job of repetition. Their logo is on the top of all pages and their colors stay consistent throughout. Therefore, it is easy to tell when you are on their site or if you have navigated away from it. The sites both brand themselves with their colors and logo.

Priceline's site has great alignment. Most of the boxes are centered and remain there. On the other hand, Expedia has boxes all over. It seems to cluttered to even see where the lines are or even where sections are supposed to end and others are supposed to begin.

Design Winner
Priceline has a better designed site. It's colors, alignment, and use of open space on the page make it nice to look at. Expedia's page has font too small, too many images/ads, and no open space.