ThemeForest is convenient because I have more choice. Next time if I need a theme, I might go to your shop.
There was 2-3 times where ThemeForest did not have what I wanted 100% so I went to WP.org's theme directory and found what I wanted.
I don't think a paid theme is better than a free theme, and I don't think a free theme is better than a paid theme.
Also if a client is willing to pay...I am more flexible.