Based off memory. Also, spoilers.
The first cour of the second season of Durarara!! (which was made 5 years prior to this one) was done well. It's story was like that of the first season but with added characters and suspense.
The animation was once again done very well.
The voice actors did a good job, and the opening was once again fabulous. The rest of the OST and ending was meh.
The characters developed more. The first cour was probably the second most suspenseful in terms of that out of the three.