My first e-cig was an eGo-T. Folks on here said that those batteries wouldn't last forever, and that I should get a backup. So I got a 510-N (bad mistake), the eGo's outlasted the 510-N. So I started looking for just what your question asks, what is the most reliable. At that time (2011) the consenses was that the Silver Bullet was the best choice. My SB is now a month short of being three years old, and still looks, and works, like new.
Having that SB, and not having to replace it every time I turned around, is what has made it possible for me to buy any PV that I wanted to try.
I learned early on that the most reliable topper was a simple atomizer. I still have atomizers that are over two years old that work just fine. But, times change, and new products become available. RDA's have taken the place of the simple atomizers, and I have an assortment of PV's that will last a lifetime. Simply put, there are an abundance of reliable ways to vape now, so take your choice.
Right now I have six PV's sitting on my desk, all six are set up differently, and I wouldn't hesitate to leave the house for the day with any one of them.