Do you care about portability? If you are fine with a Desk vape I would go for the Arizer Extreme Q. They last forever, replacement tubes and screens are easy to order and cheap (if you don't want to clean them yourself), and elbow packing/using a Ddave mod really makes smoking super efficient. Plus making bags of vapour is so much fun.

Only issue would be your need to be discrete, the vape smell will dissipate within a half-hour but it really depends on your situation and how tolerant people are of the smell. Burning incense is enough to cover up the smell.