Different strokes for different folks, as Anna said.
Personally, I mostly vape on a squonker. Because of that, I've become rather attached to single coil flavor RDAs, i.e. Psyclone Entheon, Oumier Wasp Nano, Pulse 22...
Prior to squonking, my favorite RDA was the Digiflavor Pharaoh Dripper Tank. In close second was a tie between the Wotofo Troll RDA and the 528 Custom Goon V1.
But it all depends on what you prefer.
Single coil? Dual?
Hot vape? Cool Vape?
Flavor? Clouds?
22mm, 24mm, or more mm?
510 or 810 drip tip?
Side airflow? Bottom airflow? Top airflow?
Airy? Tight draw?
So many questions it makes a really good answer tough to give...
But, always willing to try.