The Shop-Vac 90662 and 90672 disposable filter bags are similar items. They both are designed for dry pick up non-hazardous, non-toxic, non-flammable materials only, such as drywall dust, cement dust and cold ashes.
Both of them fit standard 10-14 gallon Shop-Vac vacuums with the inlet located on the tank.

The Shop-Vac categorize their bags into Disposable Collection Bags and Fine Dust Collection Bags.
The 90662 belongs to Disposable Collection Bags and 90672 belongs to Fine Dust Collection Bags.

According to Shop-Vac, Disposable Collection Bags are for fine dust and debris whereas Fine Dust Collection Bags are high efficiency filter bag for extra fine dry messes. So the difference between 90662 and 90672 is 90672 can filter finer dry messes.

Some questions and answers:

• What is my shop vac model number?
  There is a label located somewhere on the vacuum, commonly at the back or under the nozzle.
• Is a shop vac stronger than a vacuum?
  Generally speaking, a wet dry vacuum is more powerful than a regular vacuum.
• Can you reuse shop vac bags?
  It is not recommended to reuse a vacuum bag.
• Do vacuums have serial numbers?
  Yes. A vacuum usually has a serial numbers or model number.
• Are all vacuums the same?
  No. Vacuum has different types, there are upright, canister, stick, handheld and robotic vacuum. Some have more powerful suction, some have less power. Some have two motors – one agitator motor and one suction motor, some have single motor. Some use bag to collect messes whereas some use a dust cup. And there are other differences, so vacuum cleaners are not the same.
• Is a shop vac wet or dry?
  A shop vac is also known as a wet/dry vacuum.
• How often do you need to replace a shop vac bag?
  It depends. Usually, when it gets full, it should be replaced.
• How many years do vacuums last?
  It depends on the quality of the vacuum. Nowadays, there are few vacuum cleaners that can last 10 years.
• How do I know if my vacuum use a HEPA filter?
  Read product ads, manual, consult the manufacturer, etc.
• When should vacuums be replaced?
  When you find it lose suction power, or it no longer seal well.
• Do commercial vacuums last longer?
  Commercial vacuums commonly are built with more durable and better quality materials than household vacuum. However, they are also for heavy use. So, it is hard to say if they would last longer.
• Is it OK to vacuum everyday?
  Vacuum every day should be OK.
• Should you clean a vacuum after every use?
  You should and it is recommended to clean your vacuum cleaners after every use. The filter, dust cup (if the vacuum has one), and the brush roller are main parts you should clean after each use to maintain the performance.
• Is a HEPA vacuum better?
  For cleaner air, yes. A HEPA vacuum commonly can capture smaller particles than a standard vacuum and emit cleaner air. It is a better option for people who suffer from asthma and allergies.
• Is it better to vacuum fast or slow?
  Vacuum slowly theoretically would clean more thoroughly. However, it costs you more time.
• Is it OK to vacuum once a month?
  It depends on the traffic. For a usual house, vacuum once per month is not enough. Once a few days should be OK.
• Is just vacuuming enough?
  No. You should combine vacuuming with mopping, steam, and washing.
• How long does a HEPA filter last in a vacuum?
  Some last one or two years, some may last the lifetime of the vacuum.
• Can you clean a HEPA filter and reuse it?
  Many HEPA filters are washable, you can wash it and reuse it.

Here are some differences between Wen DC3401 and Dc340 rolling dust collectors you may want to know before making a purchase.

• Motor
  The DC3401 has 5.7A brushed motor whereas the DC3474 equipped with a 7.4A induction motor.
• Motor Speed
  The DC3474 has a no load motor speed of 3450rpm versus 4500rpm on the DC3401.
• Air Flow Capacity
  The DC3401 has a air flow capacity of 660cfm versus 600 cfm on the DC3474.
• Impeller Diameter
  The DC3401 has a impeller diameter of 6-inch versus 9-inch on the DC3474.
• Casters
  The DC3401 has four 1.75-inch lockable swivel casters whereas the DC3474 has four 2-inch swivel casters.
• Dimensions
  The DC3401 is smaller, it has dimensions of 34.25 in. x 13 in. x 14.2 in. whereas the DC3474 dimensions are 43.3 in. x 17.7 in. x 20.1 in..

Similarities between them:

• They are corded.
• They have four rolling swivel casters.
• They have 4-inch dust port allows for connection to woodworking tools
• Optional wall mount allows you to mount the unit to the wall.
• 5-micron zippered collection bag.
• Onboard carrying handle help transport.
• Carry two-year limited warranty.

Some questions and answers:

• Which is better dust collector or shop vac?
  They are designed for different jobs. The dust collector commonly used for large-scale dust management from woodworking machines, they can handle dust and wood chips. The shop vac is for dealing with wet/dry messes in your garage, workshop, automobile, etc.
• What is the best vacuum?
  It depends. The best vacuum is the one that meets the user’s budgets and cleaning needs. If you want to clean a sofa, then a large upright is too cumbersome for your needs, a handheld vacuum is better than the upright in such situation. Commonly, a higher price vacuum does the job better than a cheaper one. Some popular vacuum brands to consider: Kenmore, Miele, Sebo, Henry, etc.
• Is a central vac stronger than a shop vac?
  General speaking, a central vac is more powerful.
• Can you use a shop vac as a house vacuum?
  If you want, you can. But shop vac commonly is more bulky, most do not have motorized floor head, some do not have good filtration. Do the research before buying the shop vac.
• What is the best class dust extractor?
  H-Class dust extractors provide the highest level of filtration.
• Is Shark or Dyson better vacuum?
  Both of them produce a lot of vacuum cleaners, Shark price usually is lower. Both are fine.
• Are Miele vacuums worth the money?
  Miele vacuums are commonly priced higher than most of the vacuum cleaners on the market. However, the quality meets the price.
• Is 600 CFM enough for dust collector?
  600 cfm is enough for most woodworking machines.
• Is a wet vac better than a regular vacuum?
  If you want to pick up wet messes, then the wet vac is better, a regular vacuum cannot handle wet messes. If you want to pick up dry messes, then a regular vacuum is better.
• What is the highest class dust extractor?
  There are 3 dust classes: L (low risk dust), M (medium risk dust) and H (high risk dust).
  The highest class dust extractor is H class.
• What vacuum to use for ashes?
  There are vacuum cleaners, ash vacuums, designed specifically for cleaning ash.

The main difference between Karcher WV 1 Plus, WV 6 Plus and WV 6 Premium is as follows:

Karcher WV 6 Plus vs WV 6 Premium
The WV 6 Premium are almost the same as WV 6 Plus, but comes in a Premium white color, and includes some extra accessories: a narrow suction nozzle which is 6.7-inch in width for cleaning small panes, a microfiber wiping cloth for outdoor use and a Dirt Scraper for removing
heavy soiling such as dried bird droppings.

Karcher WV 1 Plus vs WV 6 Plus/Premium

• The WV 6 Plus/Premium have wider improved blade which is more flexible, clean closer to edges and floor, and help you clean faster.
• The run time on WV 6 Plus/Premium is much longer, they run up to 100 minutes versus 25 minutes on the WV 1 Plus. Longer run time allows you to clean larger areas without interrupting.
• The WV 6 Plus/Premium have more intuitive LED display which can indicate the remaining minutes of battery running time, the one on WV1 Plus does not show this data.
• The squeegee blade and the suction nozzle on the WV 6 Plus/Premium are easier to be removed for cleaning after each use.
• The WV 6 Plus/Premium come with a fast charger whereas the WV 1 Plus uses a standard charger.
• The WV 6 Plus/Premium have a larger waste water tank which holds 150ml versus 100ml on the WV1 Plus.
• The Premium is in white color whereas the Plus is yellow.

Read comparison table below for more info:

Some similarities:
They all have built in battery which is not removable for recharging. You can not use a second battery to extend the working time.
Have On/Off button.
Have only one vacuum speed.

For more details, you can download manuals from Karcher official website, here are the links if you are lazy to find the links on their website.

Karcher WV 1 Plus Manual
https://s1.kaercher-media.com/documents/manuals/raw/000/BTA-5676200-000-01.pdf

Karcher WV 6 Plus Manual
https://s1.kaercher-media.com/documents/manuals/raw/000/BTA-5765066-000-01.pdf

Karcher WV 6 Premium Manual
https://s1.kaercher-media.com/documents/manuals/raw/000/BTA-5765068-000-01.pdf