Being that battery life and vapor was listed as your top criteria my recommendation is as follows:
If you want to stay under $100 than I would go for the Janty Stick as it has a 6 month warranty, gets about double the battery life of your current penstyle and a built-in passthrough. It also uses the same atomizers as most penstyles so you will be able to have some redundancy. Several folks here have stated that the atomizers from Best e-cig (BE112) work great on the stick. There are some issues with the stick that some have experienced such as a faulty switch and leaking issues. If you were to experience these issues you've got a 6 month warranty so that will cover you for a while.
If your budget is over $100 then I'd look at the GG, the Prodigy and Screwdriver. Both the Prodigy and Screwdriver are offered in Penstyle versions, the GG offers an adapter. The GG is about $200 while the Prodigy and Screwdriver are around $150. The Prodigy is a 5v device, the Screwdriver is 3.7v and the GG is configurable in 3.7v and 6v. If you use liquid cut with VG I would avoid a 6v configuration. See this website for more info on that:
Information on the electronic cigarette, the alternative to smoking tobacco. (thanks to kinabaloo).
The price point difference between the Screwdriver and Prodigy are negligible so the real difference is warranty and voltage. There is a lot of info on the voltage issue on the board so I would recommend you search around and ask questions about that. I am not sure as to what kind of warranty Trog offers on the Screwdriver but the Prodigy comes with a 6-month warranty. These warranties do not cover atomizers. I hope that helps.