This'll be convoluted...
I became enamored of mesh rebuildables (once I figured out the wicking... using my own wick), and collected a bunch of mesh RTAs.
I'd always been a fan of top air RTAs and RDTAs for their lack of leakiness.
But that's not it...
After years of knocking/bashing pod systems, I wound up with a Skillet Box. Yeah, I consider it a pod system... It was OK, buy still not all that for me.
Then I saw the Vandy Vape Kylin M AIO. Mesh AND BB form factor AND RDTA style build deck. I jumped on that.
That made me want to reevaluate my stance on AIOs. Since then, I've acquired a Mulus, a DotAIO, a Gemini, and a Ratel.
I still can't stand dedicated/disposable pod systems/AIOs, but they AIOs with RBAs and swappable batteries have changed my mind quite a bit.
So, the winner for 2020 is the Vandy Vape Kylin M AIO as it was, for me, truly a game changer.