Sound On Sound:
Although Nuendo 5 inherits most of the functionality introduced in Cubase 5 (and now 5.5), many of Cubase's more specific features for music creation are not present in the standard Nuendo 5 package. Instead, these extras are available as part of the Nuendo Expansion Kit (NEK), which was first introduced with Nuendo 4 so that Steinberg could clearly differentiate the program as being targeted for audio production rather than for music. As a bonus, it also allowed the company to start charging users an extra fee.
The original NEK wasn't terribly exciting. It brought back the Drum and Score editors, along with four of the VST Instruments that were included with Cubase. However, given the number of nifty new features for music creation that Steinberg introduced in Cubase 5, the decision has been made to remove these from the standard Nuendo package and include them in the NEK instead. So if you purchase Nuendo 5 and expect to see plug‑ins such as Loop Mash, Groove Agent One and Beat Designer, or want to work with VST Expression, you might be disappointed.
While Steinberg have definitely added value to the NEK in version 5 with these new features, I still struggle with the logic behind the decision. I understand the company wants to distinguish Nuendo with a different set of merits; but I'm not sure anyone was confused about Pro Tools virtues' for audio production when Digidesign released version 8 and included all of the new music creation features in both LE and HD without any extra cost being applied.
At the end of the day, if you use Nuendo for music creation, you'll want the NEK. If you're already an NEK user, you'll need to purchase upgrades for both Nuendo and the NEK when moving to version 5.