There isn't a whole lot similarities between D-Frag and Hyouka.
Hyouka goes along with a romance and mystery approach with some comedy reliefs, the main male character is also different with him being all lazy, but intelligent.
D-Frag is mainly comedy with the main character being a so called "delinquent", but is actually kind.
Still they are both very good series and I suggest you watch both.
My favorite moment in D-Frag would be when Roka Shibasaki said she was actually darkness type, made me laugh a lot.