Avery is a full court pest, but he seems extremely weak when trying to push through screens, and his short height/length is what will ultimately be his downfall.
Smart is a smarter all around defender, and the fact as someone stated, that this is even being compared, shows how defensively sound Smart was coming out of college. I remember I saw a few USA basketball highlights, when Smart/Randle were playing on that team, and Jones was getting smoked by Exum. Only Payton/Smart seemed to really force and lock down Exum.
Smart has the height, strength, and lateral quickness despite Avery being quicker, to be the far superior defender in a year or so, plus the wingspan of 6'9.25 to boot.
I like Avery. I really do. But Avery isn't a starting SG. He would absolutely wreck and force ball handlers on the 2nd unit to try to adjust, and I wouldn't mind him playing 20-25 minutes close to starting, just because of his high energy/hustle, and determined defensive plays. The problem like people have said, Avery is far too aggressive, gets called for fouls, and his height/inability to fight through screens seems like it'll be a huge disadvantage.
Let me just put this out here... Bradley can guard Harden, but Smart made Harden's life miserable.
https://www.youtube.com/watch?v=hmjli8hakJY