The difference between Ridgid WD4070 and WD4080 are as follows.

• The main difference between them is the WD4080 has detachable handheld blower design whereas the WD4070 does not. The power head of the WD4080 can be detached from the unit and converted into a handheld blower with a locking blower wand, whereas the Wd4070 can also be used as blower to blow sawdust and other debris, but it uses the port and hose.
• The Wd4080 comes with a blower wand which the WD4070 does not include.
• The Peak horsepower of WD4080 is 6hp versus 5hp on the Wd4070.
• The WD4080 is 10 amps versus 9 amps on the WD4070.
• The Max CFM of WD4080 is 120 versus 110 on the WD4070.

Similarities between them:

• They are wet dry vacuum cleaners for picking up wet or dry messes.
• They are corded and have a 20-foot power cord.
• The tank capacity is 4-gallon/15l.
• They have 1-7/8″ x 7′ hose.
• The have large rear wheels and casters for smooth moving around.
• Comes with a Car Nozzle, an Utility Nozzle and two Extension Wands.
• Accessory Storage Caddy to keeps the accessories close for quick access and for tools neat storage.
• In black and orange color.
• Carry full lifetime warranty.
• No built-in drain for emptying liquids effortlessly.

Some questions and answers:

• What is a good HP for a wet dry vac?
  High HP does not guarantee strong suction. However, 5 to 6.5 HP wet dry vacuum is commonly seen in the market.
• How do I choose a wet dry vac?
  If the manufacturer provides the info on suction power, such as the number of air watts, then choose a high one.
  One more thing to consider is the filtration, check if it is complete seal system with HEPA filtration. If you want the air expels fresh, good filtration is an important factor to check.
  The other thing to take a look at is the wheels and casters, if you need mobility, wheels and casters are a must. Some shop vacuum on the market do not have wheels or casters.
  If you need to tackle a large amount of messes, you may want to consider one with big tank capacity.
• What is shop vac used for?
  Commonly used for heavy duty wet or dry messes clean up in vehicles, garage, workshops.
• Is a shop vac wet or dry?
  Shop-vac is wet/dry vacuum.
• Is a shop vac the same as a wet dry vac?
  As fast as I know, yes.
• Can I use a shop vac to clean my car?
  Cleaning automobile interior is one of applications of a shop vac.
• Can you use a shop vac for dry?
  Yes, but the filter is required.
• Can I use my shop vac without a bag?
  A bag is not necessary for most wet dry vacuum cleaners.
• Does hose size matter on a shop vac?
  Two common diameter sizes of a shop vac are 1-7/8″ and 2-1/2″, if you pick up larger debris, you need the 2-1/2″ hose, otherwise you get the smaller one.
• Can you use a plastic garbage bag in a shop vac?
  Some shop vacs use dedicated bags while some others can use any plastic bag, such as the Shark MessMaster wet dry vacuum, you can line the tank with any plastic bag (2-13 gallon) and vacuum straight into it.
• Can a shop vac pick up liquid?
  Yes.
• Do all shop vacs have a blower port?
• Most shop vacs have a blower port to enable them to be used as a blower, but not all. Some shop vacs may not have the blower function.
• How do you know when a shop vac bag is full?
  Shop vacs usually do not have a full indicator. General speaking, when it is full, you will notice a decrease in suction power.
• Can I use my shop vac as a leaf blower?
  Most shop vacs can be used as a blower, some even has detachable blower, such as the Ridgid WD4080.