We will discuss the difference between Shark NV356E and UV440 within this post.

The NV356E is a Navigator Professional model while the UV440 is a Navigator Deluxe model, the difference is slight, mostly the accessories.
Shark NV356E vs UV440
images from manufacturer

Cord Length
The Shark Navigator Lift Away Deluxe UV440 is equipped with a longer cord that has a length of 35-foot versus 30-foot on the Shark Navigator Lift-Away Professional NV356E.

Wand Amounts
For extended reach, the UV440 also comes with an extra extension wand besides the longer cord. Thus, the UV440 has 2 wands while the NV356E comes with one wand.

Included Tools
The NV356E Comes with a Dusting Brush, 2 Crevice Tool include an 8″ one and a 24″ one, Pet Power Brush, Dust Away Hard Floor Attachment with 2 Microfiber Pads (this Shark’s patented Dust-Away hard floor cleaning kit is designed for picking up the debris and particles from bare floors).
While the UV440 comes with a Dusting Brush, a short Crevice Tool, Pet Power Brush.

Pet Power Brush Difference
The pet power brush included within the UV440 is a smaller one with see-through cover while the one on the NV356E is larger and opaque.
The small one can be opened up all the way to remove any blockage or build-up around the rotating brush, while the wider one on the NV356E will not open all the way while cleaning it.
The user manuals have the illustration, to save you time to download the guide, here are 2 images including that taken from the Shark UV440 and NV356E user manuals.
NV356E Power Brush:

UV440 Power Brush:

Color
The NV356E is white while the UV440 is gray.

To sum up, the Shark NV356E comes with more accessories especially the Dust Away Hard Floor Attachment, while the UV440 provides longer reach.