Fortunately our house was built in the 90s, so I'm not concerned with asbestos.

Sanding = dust, a nasty and (usually) long-lasting issue if one has a forced-air HVAC system. As per Patricia, a skim coat will be necessary...and good luck finding someone who is really good applying it.

I also think sanding would be messier than scraping with water. We did our entire house ourselves and even the painted ceiling can be scraped down with some effort. We were able to smooth out any gouges and tape lines and just paint over the ceiling without skimcoating. We were lucky. I am not sure sanding will help you avoid what's underneath unless you're going for a semi-textured knockdown ceiling.

I suspect the sander uses a vacuum attachment and filter of some kind. I've seen the a "filter" was water that captured the dust in water completely. But you need to ask the people who will be doing the work how they will capture dust. My sister has that done and they taped off with plastic all other rooms, floor, walls, HVAC vents so no dust got anywhere.

I think Izzy Mn might be right. There is a company in our area that refinishes hardwood using a similar vacuum method, promising 99% dust free. I’ve heard it works.

That's exactly what the contractor said. He showed us photos of how he puts up plastic everywhere, and the super duper sander/vacuum that he uses. He's satisfied me that he'll capture the mess; I'm more concerned with being satisfied with the ceiling afterwards and not having any surprise additional costs.

He cant make a guarantee that you wont need a skim coat, until everything is all removed. Popcorn was sprayed on, because it was quick and easy and left a finished ceiling, so that not much time had to be spent, getting ceilings perfect. If they had done a perfect drywall job, they wouldnt have used the popcorn, so when you have it done, plan for a skim coat, and consider yourself very lucky, if you dont have to have it done.

Festool makes a system that would do that.

If they had done a perfect drywall job, they wouldn't have used the popcorn

That, or more likely, the contrapositive -- if they hadn't used popcorn texture to hide the slop, they might have done a better job finishing the ceiling drywall.

Or not, as I've seen in some recent construction. :(

Wet removal with snow shovel has always been my preferred method. I don't get the skim coat issue. You're gonna put some kind of texture or brocade on the ceiling anyway, right?

OP hasnt said, if they were going to have another texture applied, but most people that remove popcorn, are removing it because, they want smooth ceilings, so assuming that is what they want to do.

Not to be a wet blanket but there is actually no law in the US prohibiting the use of asbestos in products. It's just that most manufacturers don't do it because of the potential liability. It would not cost much to send some to a lab to be sure. Or, consult an abatement contractor and see what they say about it.

We didn't plan on doing another texture if the popcorn was removed.