Thomas was all heart, with obvious deft shooting touch, and body control. But Irving is more skilled, and his game as posters have said, leads to contrived longevity. He plays the game at a pace he's comfortable with, darting in and out, and they have similar hesitation and crossover dribbles. They are both actually really similar players, but Thomas tends to use his body more and initiate contact.
Irving is a better shooter, and I suspect in Steven's system over time, and once he gets immensely comfortable, will be shooting twice the amount of 3's, and making honestly twice as many as his career averages. IT averaged 8.3 3PA, which was almost twice as much as his tenure during SAC.