What I have found to be the best, is only the best for me. Everyone will find what works best for themselves. I've used quite a few. I've even used heavy brown constrution paper. (It's like heavy duty market bags. In fact, I've tried every kind of surface I come across that is different, just to see what happens. I have also found that my favorites are based on what I what to accomplish. For instance, if I am painting a portrait or on a piece that requires minute details, I use Arches hot pressed watercolor paper. This comes in several sizes of tablets and sheets. Usec140# or better. This small study was done with watersoluble oil pastel. Perfect choice, for me, is the Arches HP 140# WC paper.
. I've used other brands and they didn't seem to hold up to the heavy workout I demand. So I tend to remain loyal to Arches. But for the most part I truly enjoy using Arches Oil Paper. Wow! What a surface for oil pastel. Arches oil paper comes in different sizes of tablets or in sheets. Not totally smooth, plenty of tooth to hold layer after layer. Yet, it's still smooth enough to get most of those pesky, tiny details. For me it's the best choice for plein air work. Layering and blending, as with this piece, was made eaisier with my choice of paper.
If I am working in a piece that I want to resemble an oil painting upon completion, I use Canson Canvas paper. The surface resembles a fine stretched canvas. The finished piece shows this surface a bit in some work. This really shows up in the board fence on this piece. So, again I say, Choosing the best paper is subjective.