With a pit, I would say this, if you make a mess i.e dropping the oil from a car and you miss the pan, then its an easier clean and limited to that immediate area, and as it's in a work area that you expect to get dirty you won't have an OCD hissy fit and nothing in the vicinity gets dirty in the process.
If you drop any tools, nuts bolts etc..... then they don't roll away and disappear to never never land. They are in the pit and easy to find!
Access to the underneath of a car I've found really quick and easy and being able to see all the bits of the car as a whole is advantageous. From a safety point, the car is still on the ground (like a four post) so it ain't falling anywhere. In my case, I simply drive over the pit (with the sleepers still in place) then I remove a ventilation grill, step on to a permanent ladder thats below and systematically remove the sleepers one by one. Takes all of a few minutes to gain full access and I'm "up skirting" her (see picture above) before you know it.......
For me, having a pit makes the work just as easy as a four poster with no floor surface area being compromised. If I wanted to use a gearbox jack let's say to do a clutch,then that is do-able, as the pit is deep enough and wide enough to accommodate having that tool in there. Having railway sleepers in place allows me a strong base should I park a car on top of it and because they are in set cut sections, I can choose to remove some or all depending on my needs, they are also strong enough to support a car, axle stands, jacks etc. So if I need to ever do wheels off stuff such as discs and brakes or let's say remove an exhaust, but still need below access, then that is possible too.
The advantage of a fourposter, Point 1: it's a cleaner way of working, push a button the car goes up. Point 2: height can be adjusted to the user. (i.e in a pit it's a set height and a short ***' like me sometimes needs to use a step to reach some bits buried higher up). Point 3: another car park space has just materialised! The only thing to watch here is grime and oil dropping on to the car below, so cover the car underneath. It doesn't bare thinking about if you've got leaks from brake/clutch etc and fluids are dropping on to your other pride and joy.
The only tricky job I can think of with the four poster is.... It might not be easy to do a removal of a suspension strut. But then you'd use jack and stands for this if no two post lift is available.
If you go down the route in having a pit, make sure you install some sort of lighting and a power source outlet (somewhere close to enable you to plug a power tool or two). A way to get in/out i.e build in steps or more space saving/cost idea....just put a ladder. The ventilation grill I mentioned above in the 2nd para is to allow the pit to breath and prevent humidity when you're not using it (i.e when all the sleepers are in place).
If none of the above works for you then.......
Step one: Open door of your Magnifico Maser
Step two: Turn key of said car,
Step three: Start engine and let warm,
Step four: Drive down to your favourite Main dealer or Indie.
Step five: Wait in luxury client area with lovely coffee and beautiful people.
Step six: Pay said Main dealer or Indie......
Step seven: Drive home in your recently sorted Maser.
Step eight: (Optional) No need to have a shower after work done.
Hope this was of use..