I figured that I would chime in. I had kept my snakes in glass tanks for years, before we built our rack. I had my adult female in a 40-g low long breeder tank, with a screen lid.. and my others were in 30g and 20g tanks.. I also used a 10g tank for a time. But the big thing is, that my room was heated around them. I could never let my snake room get below the lowest temperature that I wanted for the snakes in their tanks. As long as this rule was kept, I guess that things would be fine. Sure, this was no big deal, as it still holds true for my tubbed snakes now. But.. I always had to wrap saran wrap over their screen lids for humidity retention, as the heating element I used (space heater) made the room Uber Dry. (danged thing still does! But it's just in our bedroom, with no snakes, and just gives me horrific bloody noses overnight if I forget to fill the humidifier..) So the animals being harmed are just me and my husband; nothing important
Now, I use a rack; homemade out of melamine, with 41-quart tubs (smaller ones in the top shelf that hold a juvi and small adult male.) I have a gas fireplace in their room, which keeps the temps stable outside if for some reason we turn down the central heat of the house. It dries out the air negligibly, so if I had tanks, it'd be a rip to keep the humidity up especially when I jack it up in shed times. The tubs retain it very well..
But the biggest draw for them, to me, is the ease of lifting for cleaning. Granted, I am not a lightweight; I have a farm-girl giant-calves body. But lifting is not my thing. Lifting tanks to completely sanitize them would kill my back. Lifting tubs is simple.
Now, I am not saying that something is right for me because it is easy; that would be omitting out the health of the animal contained within. I like the tubs because of their opaque nature; the snakes don't need to be gawked at by my cat walking around all day I do have my BCI living in a display-type setup with glass walls and a sliding front door; it is a rip to clean!
I think that the main thing is to do what works for you, consistently and with right-n results for temperature, humidity, and space. I won't slam anyone for using tanks, or homemade display showcases, as long as the animal is not being overstressed by passers-by and glass tappers (this could happen in tubs anyway..)