In informal terms the difference between dex and deb

is that dex is dextromethorphan while deb is debutante.

As nouns the difference between dex and deb

is that dex is an order or factor of ten. Used both to refer to the function $\backslash mathrm\{dex\}(x)\; =\; 10^x$ and the number of (possibly fractional) orders of magnitude separating two numbers. When dealing with log to the base 10 transform of a number set the transform of 10, 100, and 1 000 000 is $\backslash log\_\{10\}(10)\; =\; 1$, $\backslash log\_\{10\}(100)\; =\; 2$, and $\backslash log\_\{10\}(1\; 000\; 000)\; =\; 6$, so the difference between 10 and 100 in base 10 is 1 dex and the difference between 1 and 1 000 000 is 6 dex while deb is debutante.

As an initialism DEB is

dynamic energy budget (see Wikipedia article.

As a proper noun Deb is

abbreviated form of the female given name Deborah.