Vivi Nova's are top coil. Protank is a bottom coil. It's a matter of taste (top coil generally gives a warmer vape). Nothing wrong with either tank, I have both and both work fine. The Vivi Nova's wicking system can be a PITA because of the long wick and the fact you have to do the "tilting" thing.
This is why I never use the Novas anymore. I just stick with the protanks (which along with the Nautilus is the best tank on the market that isn't an RBA). I get good enough flavor from the protank and don't have to bother with the tilting or the cleaning of the Vivi heads.
EDIT: As for glass vs. plastic, it's glass all day long. I am surprised any vendor bothers with plastic tanks anymore. Pyrex is cheap and can be easily protected by designs like SMOK's Aro. So if your question is whether it's worth buying a new glass Vivi and replacing your plastic ones, the answer is yes, it is definitely worth it.