New to this site.

Welcome!

Is it an external or software difference?

There is no software difference, and whether or not is says "empeg" on boot is changeable, so that's not how you tell. The differences between the two models are listed as the very first item in the very first section of the Empeg FAQ here. Spend some time going through that, it's up to date (I just added an entry minutes ago) and very complete. Some even consider it to be interesting reading.