2 or 4 post lift?

Really depends on what you'd want to use it for.
As someone who has spent 35+ years under car lifts they both have advantages and disadvantages.
If it's purely to store a car then either would do the job but I fully agree with earlier comments about suspension being left on full droop could stress the ball joints and the rubber components like CV boots and ball joint covers. Would it hurt the shock absorbers on full droop? Not sure, never tried leaving them in that position but could go either way there.
Cars parked on wheels for any length of time can damage the tyres as it creates a flat spot where the tread, and hence the steel plies are held in an unnatural (for them) position so it can create a "flat spot" in the tyre. This would indeed be avoided with a 2 post lift, but nothing stopping the car being rolled back a quarter wheel rotation every few weeks on a 4 poster, would help to move the brake pads from sitting in the same location on the discs too to prevent them sticking to the disc face.

One thing that hasn't been mentioned much yet is safety.

2 post lifts are far more dangerous than 4 post ones, yes ropes can break on the 4 post ones but there are mechanical arrestors on them to stop it falling more than a few inches. The Bradbury 2 post lift we have at work has (like most of them) a threaded bar up inside each post which rotates inside the arm supports which raises the lift, the bar across the bottom under the little ramps (sometimes above) contains a gear shaft that rotates the other side lift, a motor drives just one side.

The issue with that is the nut wears on the lifting arm so needs careful measuring for wear to prevent the ramp slipping down the threaded bar inside the lift post. Sound implausible? Ask me how I know, because I was stood 2 feet behind a car being raised on the lift when one side collapsed dropping like a stone. Luckily it had only raised a couple of feet and wasn't at full height or I wouldn't be here to tell the tale.
OK a rare event but I just don't trust them anymore which is why it hardly gets used anymore despite them being very handy for doing suspension work as access is far better than with a 4 poster.

Also consider with a 2 post lift how unstable they are, the ramp will move considerably as it flexes on it's frame, as much a s3 or 4 inches of travel at either end of the car up and down! You also really should ratchet strap the car to the lift to prevent it falling off, check YouTube for the many disasters...

As I say though, depends what you are going to use it for.

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