Some differences between Shark ZU632, NV752, LA555, LA702, LA502 and AZ2002:

• Brushroll Design
  The NV752 has a traditional brushroll,
  the ZU632 has a self-cleaning brushroll,
  whereas the LA502,LA702,LA555 and AZ2002 have one soft roller and one Powerfin roller with self-cleaning feature.
• Brushroll On/Off Control
  The LA555,LA702,LA502, AZ2002 and ZU632 do NOT have a brush off setting, the rollers keep spinning in all floor settings.
  While the NV752 is the only one that you can turn off the brushroll when setting to Hard Floor.
  So, if you want one with a brush on/off button that will not make you worry about scratching your hard floor, have a look at the NV752.
• Lift Away Type
  The NV752, AZ2002 and ZU632 feature Powered Lift Away whereas the LA555, LA702 and LA502 features Lift-Away.
  The difference between Powered Lift-Away and Lift-Away:
  Powered Lift-Away allows you to lift the pod and use the handle/wand with a motorized nozzle/tool whereas the Lift-Away only allows you to use non motorized nozzles/tools when detaching the pod.
  Obviously, the Powered Lift-Away models are more versatile. Especially when you want to use the powered nozzle to clean under furniture or use motorized tool to clean upholstered surface.
• Power Control Location
  The NV752, AZ2002 and ZU632 have the power control and surface selector on the handle for easy reach whereas the LA555, LA502 and LA702 have the control on the top of the pod.
  Control on the handle is more convenient when you want to turn on/off the vacuum and switch between surface settings.
• Headlights
  The LA555, LA502, LA702, AZ2002 and ZU632 have headlights on the floor nozzle whereas the NV752 is the only one that has lights on both floor nozzle and handle.
  Headlight on the handle can help you clean low light spots such as nooks and crannies with handle and tools.
• Cord Length
  The LA502, LA702, NV752 and ZU632 have a 25-foot cord whereas the LA555 and AZ632 have a longer power cable which is 30-foot in length.
• Suction Control Slider
  The NV752, AZ2002 and ZU632 do not have a Suction Control Slider to allow you to adjust suction to clean different surfaces.
  Whereas the LA555, LA502 and LA702 have a suction control slider located on the handle
  allows you to adjust the suction depending on your cleaning needs.
  If you are one of those who want to adjust the suction little by little, you may want to consider the LA555, LA502 and LA702.
• Dust Cup Capacity
  The AZ2002 has a dust cup that holds more than the other models.
• Odor Neutralizer Technology
  The LA702 and LA555 feature Odor Neutralizer Technology that helps guard against bad odors inside the vacuum for a better smelling home.
  Whereas the others do not have the ordor neutralizer cartridge.

Suction Power
Want one that will get you impressed by the suction power? Try the AZ2002, it has powerful suction.

They have some similarities too:

• Corded and Bagless.
• Anti-allergen complete seal system with HEPA filter to trap allergen and dust, and expels fresh air.
• No automatic cord rewind.
• Swivel Steering for moving around smoothly.
• Lift away pod allows you to clean high and low areas more conveniently.
• Come with tools for different cleaning jobs.
• Carry 5-year limited warranty.

Some questions and answers:

• Which Shark vacuum is the highest rated?
  You can have a look at the Shark NV360, HV322 and NV752.
• Which brand is better Shark or Bissell?
  Both have hot selling items, which is better depends on your needs.
• Are Shark vacuum cleaners made in China?
  Yes. Shark vacuum cleaners at this moment are mainly made in China.
• Is Bissell a Chinese company?
  No, it is an American company.
• Why are Shark vacuums so popular?
  This may be because of Shark keep produce various vacuum cleaners that meet customers’ cleaning needs. And they also have good marketing strategy.
• How long do shark vacuums last?
  It is hard to give an answer. Each vacuum has different build quality. Commonly, if there are no defective parts, they should last for a few years. If it is a cordless one, the battery usually will not have that long lifespan. Battery usually carry one or two year limited warranty.

The difference between Shark ZU561, LA322 and LA502:

• Brushroll
  The main difference between them is the Brushroll design.
  The LA322 uses a standard brushroll.
  The ZU561 uses a self-cleaning brushroll, they name it Zero-M Technology™. According to Shark, the design actively removes hair wrap from the brushroll while you vacuum.
  The LA502 equipped with self-cleaning DuoClean Powerfins. The DuoClean design means there are two different rollers in the floor nozzle for cleaning floors. The Powerfins design means one of the rollers uses silicon fins to replace the bristles. According to Shark, the Powerfins deliver non-stop contact on the carpets and floors.
• Headlights
  The ZU561 does not have Headlights whereas the LA322 and LA502 have headlights on the floor nozzle to help clean low light spots.
• Color
  The The ZU561 is red, the LA322 is black, while the LA502 is grey.
• Accessories
  The ZU561 comes with a Duster Crevice Tool, a Hair Removal Multi-Tool, and a Wide Upholstery Tool;
  
  

  image from ZU561 manual

  
  the LA322 comes with a Crevice Tool, a Dusting Brush, and a Pet Power Brush;
  the LA502 comes with a Crevice Tool, a Pet Multi-Tool, and a Self-Cleaning Pet Power Brush.
  
  

  image from sharkclean.com

Similarities between them:

• Lift-Away Design – The detachable pod can be lifted away to help clean stairs and high and low hard to reach areas, such as stairs and windowsills.
• Anti-Allergen Complete Sealed System captures and traps over 99.9 percent of dust and allergen (based on ASTMF1977 down to 0.3 microns or larger).
• Swivel Steering for maneuvering easier around corners, furniture, and more.
• Suction Control Slider for adjusting suction power to clean different surfaces.
• No automatic cord rewind, cord needs to be winded manually.
• No brushroll On/Off control, brushroll spins in both Hard Floor setting and Carpet setting.