Prot is looking more enticing for leveling through the rest of Legion and into BFA, and for going back and doing older content and such. He had a video where he used Azerite traits and Pally abilities to solo tank Mother in Uldir. One guy constantly figures out ways to solo tank raid bosses.
I would lean towards paladin tho, as they do more damage. I main prot paladin and alt BDK, both feel incredibly strong in world content.
Is it the mighty paladin now with Azeroth armor absorbs, avengers shield, and multiple utility spells to get themselves healed up quick? I leave out dh, warrior druid and monk because from my experience and what I have been reading they lack the self heals without healer support to sustain themselves over long periods of time. Assuming equal gear levels, what tank is king of the solo in BFA? Are blood DKs still the king with their self heals, blood shield and high uptime CDs? I could easily solo world bosses given enough time.