The xB is also not very wide, although it is pretty tall for a car. Still, total drag is the square feet of frontal area times the coefficient of drag. For comparison:

Width and height, in inches
2007 GM Tahoe: 79.0 x 76.9
2006 Ford 500: 74.5 x 61.5
2007 Toyo Camry: 71.7 x 57.5
2006 Honda Civic: 67.5 x 56.3
2006 Pont Vibe: 69.9 x 62.2
2007 Honda Fit: 66.2 x 60.0
2006 Scion xB: 66.5 x 64.6

Other than the Tahoe, the xB is the tallest. In fact, quite a lot taller than the Camry and Civic. I imagine that's part of what makes it popular though since all that height translates into tons of interior room when transporting tall, bulky items. Still, one would imagine the Honda Fit, being about 4.5 inches shorter and fractionally narrower with a likely lower cD has good reason to be listed as more fuel efficient. Seeing that both the xB and Fit have about a $14,000 base price and the Fit is EPA rated 15% more fuel efficient, I'd personally lean towards the Fit.