There are many good, valid reasons for Dell to promote the XPS 15z, but one of them should not because it’s the thinnest 15-inch laptop on the planet – because it isn’t.

Dell’s advertisement for the XPX 15z reads: “Just 0.97″ (24.68mm) at its thickest point, XPS 15z is the thinnest 15″ PC on the planet*. It’s also incredibly tough and lightweight.”

That little asterisk led to small print that states: “Based on Dell internal analysis as at February 2011. Based on a thickness comparison (front and rear measurements) of other 15″ laptop PCs manufactured by HP, Acer, Toshiba, Asus, Lenovo, Samsung, Sony, MSI. No comparison made with Apple or other manufacturers not listed.”

Convenient then, that the comparison against the MacBook Pro unibody was avoided, as Apple’s offering is 0.95-inches in thickness.

The lesson here is simple: it’s easy to be the best on the planet at something as long as you’re selective about your comparison pool.