From my own personal experience, I prefer glass over plastic.
I suppose it really depends on your area, but as it can get hot and humid in Sydney, particularly in the summer, the plastic tubs just did not work at all.
When my Woma was in a plastic tub (for a period of 48hrs) during a mild Spring day, even with ventilation holes drilled every 1.5cm across the entire length of the tub, it still rained in there. Took water out- still same effect. Hot, humid and reaching over 40 degrees despite the day being not much over 25.
Luckily I had on hand (and all set up as I had first intended to buy a larger animal) his 1m glass enclosure. Put him in there and everything went smoothly.
Glass tank, even in the middle of winter kept at 32 degrees on the hotspot throughout the day.
Now in summer I struggle to keep the temps down if anything. No insulation or anything- just a nice glass enclosure.
Snakes are a bit cotton wrapped if anything these days- it's totally and completely natural for them to experience fluctuating temperatures throughout the day, where on earth are you going to find a hotspot of exactly 33 degrees day and night?
My snakes have improved dramatically ever since I set a day/night cycle for them. I let nighttime temps drop to whatever the room temperature is, and turn the heat back on in the morning. My previously picky Stimsons hasn't missed a feed since I made the change, and is much more active during the night, putting on more muscle tone and in general looks better.
youve got to remember Aussie snakes are bred tough. Nighttime temps in many places where snakes reside can drop below freezing- yes the residual heat from the day keeps them warm, but my tanks will stay around 25degrees until about 3am where they drop to room temp.
Again, depends on your own personal preference, local climate and species of snake