I think across all three formats, Williamson is the most consistant performer. Williamson can score a tough 100 in tests, and destroy any attack in the limited overs, and do so effortlessly. He is better than ABD (in the past year) if you ask me. Yes he is moer consistant than Smith. And I think Williamson is a match winner however you look at it.
One bad Year for ABDV doesn't mean He can be beaten by someone like Williamson, who is a very talented batsman, but still is in his learning days.
By match winner, I meant a big game, big pressure player. He's won way more matches for India under difficult circumstances than Williamson.
*remembers his century against Pakistan when India was 18-1 in CWC'15
*remembers his knock against Sri Lanka when chasing 350 odd runs in Australia
*remembers his knock against Australia when chasing 350 odd runs in India
*remembers his knock against Pakistan when chasing 330 odd runs in Bangladesh (Asia Cup 2012)
*remembers his knock against Pakistan when India was 59/3 in WT20 2014
*remembers his knock against South Africa when chasing 170 odd runs in WT20 2014 Semi-Final