Both feature a stylish, jazzy American atmosphere paired with fun, experimental storytelling - think unusual cinematography, out of sequence events, following multiple groups of characters at once, etc. They're very similar in feel/tone, so if you love one, you'll definitely like the other one too.
Both have that American vibe with a jazzy urban feel to it where violence and destruction happen frequently as if they are the norm of everyday life.
These shows also have a large array of unconventional characters who have different back-stories which eventually intertwine with one another until it eventually unravels and converges into a single event that affects everyone around them.
I would see Kekkai Sensen as the Baccano &/ Durarara in a distant future setting.
You´ll never know what´s going on until the very end
Both take place in a fantastical New York City, with some cool action and a jazzy soundtrack you'll love. Kekkai Sensen is modern-day urban fantasy with a city flooded with mythical creatures living beside humans, where a particular organization performs some crazy action sequences to keep them in line, while Baccano! is more subtle with a non-linear narrative, historical setting during prohibition and great characters, half of which are immortals or in the mafia or arguably insane. If you like one, you'll definitely see something you like in the other.
Supernatural happenings going on in early 20th century New York. Both shows have great jazz-influenced soundtracks and plots that are interesting but hard to track.
Although they are set in different time, both are set in America and has the American vibe in it. Like Durarara and Baccano, Kekkai Sensen has a non-linear storyline. Both also has awesome battles and has a large cast of characters. Kekkai Sensen is basically Baccano of the future.
The pace and the storytelling is the same. If you liked the legendary baccano and Durarara there's a good chance to like Kekkai sensen.
Both series have characters with supernatural powers, and are set in an American setting, though one (Baccano) is set in the Prohibition era, the other (Kekkai Sensen) is set in some fantastical future with aliens. Both series are fast-paced urban fantasies with a large cast of characters with great chemistry. Both are backed with a glorious jazz soundtrack and perfectly suits the series energetic vibes.
Both have a very similar feel as in the tone. The OSTs are incredibly similar. Both are incredibly complex and at times hard to really understand. Both take place in NYC. Both involve underground organizations (though Baccano! is mostly about gangs) and both are incredibly fun.
Here are the similarities:
+ Both shows take place in NYC (BBB is basically the Baccano of the future)
+ Both shows have supernatural elements that makes the setting chaotic
+ A ridiculously large cast
+ Jazzy music
+ Same VAs both sub and dub
+ Chain from BBB literally has the clothes of Ennis, the looks and a similar name to Chane, the voice of Nice in Japanese and the voice of Rachel in the dub (the last 4 are all Baccano characters)