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Both of these 2 Shark Rocket series are Ultra-light Upright vacuum cleaners.
The Shark Rocket Complete with DuoClean HV380 Series includes several models such as the HV380, HV380W, HV381, HV381C, and HV382.
The Shark Rocket DeluxePro HV320 Series also includes several models such as the HV320, HV320W, HV321, HV321C, HV322, and HV324Q.

The main difference between the HV380 and HV320 series is the floor nozzle design.
The HV380 Series features dual brushrolls, a soft velvet brushroll and a bristle brush, to clean small, large, and stuck-on particles from hard floors and carpets, they call it DuoClean Technology.
While the HV320 series models only has a bristle brushroll. However, the HV320 models can use the HARD FLOOR ATTACHMENT that will not work with the HV380 models to clean hard floor surfaces.
With the HV380 models they do not require this tool as they have the soft roller on the floor nozzle for cleaning bare floors.
Maintaining the Brushroll.
It is easier to remove anything that wrap around the brushroll on the HV380. You just press or slide buttons to remove the rollers from the HV380, whereas the HV320 requires you to use a coin or other tools to unlock the three locks on the bottom of the floor nozzle to access the brushroll to check for or remove any blockage.
And the rollers of the HV380 series are removable for cleaning up whereas the brushroll on the HV320 series is not removable.

Power Specifications
HV320: 120V, 60Hz, 500W, 4.2 A
HV380: 120V, 60Hz, 600W, 5.0 A

Weight
The HV380 is heavier than the HV320.

If you want to learn comparison of specific models, such as hv322 vs hv382, the accessories included are the only thing to be added to the above comparison info.
Take HV322 and HV382 for example:

HV322:
HV322 name may be Shark Rocket TruePet Ultra-Light Upright, or Shark Rocket Deluxe Pro Ultra-Light Upright.
Its early version may include: a Duster Crevice Tool, an Upholstery Tool, a TruePet Mini Motorized Brush, a Dust-Away Hard Floor Attachment with Washable Microfiber Pad, a Flexible Hose, an Onboard Storage Clip, a Wall Mount and a Storage Bag.
But now it may come with a Pet Muti-Tool, a Duster Crevice Tool, a Multi-Angle Dusting Brush.
Or a Pet Muti-Tool, a Duster Crevice Tool, Hard Floor Hero Attachment(does not use pads).
Or a Pet Muti-Tool and a Duster Crevice Tool.
Or a Pet Multi-Tool, a Duster Crevice Tool, a Multi-Angle Dusting Brush, a Hard Floor Hero Attachment, and a Wall Mount Storage Hook.
etc.

HV382:
Like the HV322, there used to be a HV382 version came with a lot of attachments: an Onboard Tool Clip, a Duster Crevice Tool, an Upholstery Tool, a Dusting Brush, a Wall Mount, an Under-Appliance Wand, a TruePet Mini Motorized Brush, a Hair-Removal Tool and an Accessory Bag.

But now, it seems that this version is not available any more. It now comes with less tools.
It may include a Duster Crevice Tool, a Pet Multi-Tool, a Wall Mount, and an Onboard Tool Clip.
Or it may include a Pet Multi-Tool, a 12″ Crevice Tool, a Wall Mount, and an Onboard Tool Clip.

The included attachments may be different when purchased from different retailers. And may be different from time to time even purchased from the same retailer. And it seems that no retailer offer a package that includes the Mini Motorized Brush which many pet owners like now.
They have many similarities.

• Two Speed Brushroll: Bare Floor, Area Rugs and Carpets.
  Bare Floor, Area Rugs – The rollers spin slowly to clean bare floors and delicate area rugs.
  Carpets – Rollers spin faster, working to pick up debris below the surface of your carpets.
• 2X dust cup capacity versus HV300.
• Fingertip controls for carpet and bare floor cleaning.
• Can convert into a Hand Vacuum.
• LED lights on the hand vacuum and nozzle to reveal hidden debris.
• Swivel Steering.
• Onboard Accessory Storage.
• Can be mounted on wall.

You can read manuals to learn more difference between Shark Rocket Complete series HV380 vacuums and Shark Rocket DeluxePro Series HV320 vacuums.
Shark HV320 Manual – http://www.sharkclean.com/include/pdf/manual-HV320.pdf
Shark HV380 Manual – http://www.sharkclean.com/include/pdf/manual-HV380.pdf