I do the research and make a comparison table below to display some difference between MOOSOO K17, K20, K23, K24, M24, XL-618A, XL-618, M8-Pro and X8 cordless stick & handheld 2-in-1 vacuum cleaners.

images from imoosoo.com

P. S.
Though I try my best to collect and provide the accurate information, MOOSOO keeps upgrading the vacuums constantly, so the specifications may change from time to time, and sometimes may be outdated. Please always check product details on their official website before buying, or contact their customer service if you have any questions about the vacuum you want to buy. You can contact them via https://imoosoo.com/pages/contact-us.

Some major differences that you may want to know:

• Suction Power
  I think this is one of the most important factors that you will consider when buying a vacuum. The M24 has the most powerful suction at Max setting which generates up to 26Kpa suction power.
• Battery
  Some models have detachable battery that allows you to charge on or off the vacuum cleaner, so you can have one in use and one charging to extend cleaning time when needed, such as the M24 and XL-618A; certain model only allows you to charge the battery when attaching the battery to the vacuum, such as the K17, you can not charge the battery alone; while the K23 has a built-in battery which is not detachable.
• Charge Time
  When buying a battery powered vacuum cleaner, the charge time and run time are also important.
  The M24 takes the least time to fully recharged, commonly 3 to 3.5 hours, while the other units take from 4 to 5.5 hours to charge.
• Run Time
  They commonly run like 10 minutes at high speed setting and 30 to 40 minutes at low speed setting.
  K20 has the longest run time at low speed which is approximately 40 minutes.
• Bin Capacity
  All of them are bagless, so they use dust bin for collecting. Though stick and hand held vacuums usually have small bins, the bin capacity sometimes differs greatly.
  The K17 only holds 400ml to 500ml while the other models hold 1100ml to 1300ml.
• Power Modes
  The K20 and K23 have 3 power settings while the others have 2 settings.
• Wand
  Some models, such as the K17(upgraded version), XL-618, M8-Pro, X8, come with a adjustable wand while some models have a straight tube., such as the XL-618A and M24. However, MOOSOO sometimes may upgrade the package. So always make sure what are included before buying. Same to other accessories.
• Hose and Mini Motorized Tool
  Only certain models include the hose and Mini Motorized Tool. At this moment, the K17(upgraded version) and M8 Pro come with the hose and Mini Motorized Tool, the M24 includes the hose, while the other models do not come with these tools.
• Filtration System
  The K17,K24,XL618A,XL-618 and M8-Pro feature 4 Stages High-Efficiency Filtration System while the K20,K23,M24 and X8 have 5 Stages High-Efficiency Filtration System.
  Not sure how much difference they result in.
• HEPA filters
  The K20, M24 and X8 come with an extra HEPA filter while the others include only one.
• Noise Level
  There is also a bit difference on the noise level. The K20 is the quietest one while the K23 has the highest noise level.

Specific comparison:
MooSoo XL-618 vs XL-618A what’s the difference?
XL-618 is an upgrade of the XL-618A, it uses a telescopic wand instead of a straight wand.

Similarities:

• All of them are battery powered stick and handheld vacuums.
• All of them have headlights to help illuminate dark areas and reveal hidden dust.
• They On/Off button, not trigger type control.
• They have motorized brush roll which cannot be turned off.
• They do not have carpet pile adjustment.
• They carry one year limited warranty.
• Some models used to have 2-year limited warranty, but now all have only one year.

If you own any of these MOOSOO vacuums, please share your experience or review below to help people make an informed decision.