We have had a 4 post lift since 1990 and have used 2 post lifts in the past.
4 post advantages:
Safety. I know that a 2 post is suppose to be safe, but having see the arms on 2 post lifts slip and vehicles sway and rock when worked on makes me nervous, especially when you have seen a vehicle slip off one or more arms.
Drive on, drive off - a 4 post lets you drive on and off, so no time is consumed to crawl under and make adjustments set the lift points, go up and check, down, and adjust.
Ramps offer more flexibility - and this is the big advantage that your imagination can wonder endlessly with. You can place a jack across the ramps and use it to position a gearbox or an exhaust. You can weld onto the ramps to make attachments for a frames with cross bats to suspend an engine while you make motor mounts. This type of versatility is just about endless.
Working outside: A ramp lift can live outside as long as you change the hydraulic oil twice a year.
Other uses: If you have a problem to solve the 4 post lift comes in handy. Putting a roof rack on or off. Park a vehicle in front or behind it and install or remove a roof rack with 2 people by carefully moving it off or on which minimizes the required lifting.
You need to lift a crate or something heavy out or into a Sanky. Put a strap or chain around the item and around one of the cross bars and raise the lift. Likewise you can use it to lift an item out of the back of a pickup or trailer, drive out from under the lift and then lower the engine onto a stand or crate onto some moving dollies so it can be pushed around.
4 Post disadvantages:
You cannot do any suspension work because you need all 4 wheels. If you try to jack up a vehicle on a ramp the vehicle can move off the ramp and slide off,
The vehicle has to be running to get up the ramps and up onto the lift. Pushing it is terrible. This can be overcome with a 120V hand winch which reduces the inconvenience.
You have to pay strict attention. Your situational awareness and powers of observation need to be in use at all times as it is easy to lock one corner while the others remain free when lowering and the whole ramp can get at dangerous angles. Pay attention at all times.
The cables and pulleys need inspection and maintenance - The cables stretch and fray with time and have to be replaced. The pulleys have bushings that wear out with constant use and need to be replaced.
I won't go into the advantages of the 2 post. They work if you are careful and are fantastic for suspension work.
They lack the versatility of a 4 post lift for the reasons stated above.
Generally, but not always a 2 post needs to be inside and this often rules out a typical garage because of the height, but a 4 post is fine sitting on a concrete slab, outside, next to your garage.
