Apple Watch Nike+ Series 3 models feature include a Nike Band, exclusive Nike watch faces (along with the standard Apple Watch watch faces) and closer integration with the Nike+ Run Club app. The Nike watch faces include a permanent complication / shortcut for launching the app.
Otherwise, the models have the same internal hardware features as the comparable model (case material and GPS or GPS + Cellular version) and the same standard features of watchOS.
The Nike+ Run Club app can also be installed on other Apple Watch models.
Note that Nike+ models are only available in aluminium case versions, with Ion-X glass. Other Series 3 models offer the option of a stainless steel case and sapphire crystal (or ceramic case, for Apple Watch Edition).