Re: Plastic or glass base?
The big difference between glass and plastic is that glass will insulate better and keep the water cooler in the vase. Acrylic is more durable in the case that you drop it or such.
One note, I would not recommend that you place your acrylic vase in the freezer for 2 reasons. 1. It wont hold the cold for very long once you pull it out and 2. It may fracture.
We own multiple hookahs and from our experience Acrylic tends to fracture over time if exposed to intense heat changes (i.e. ice in the vase while smoking outside on a hot day.)
Hope this helps.