DS9 and B5 came out at roughly the same time and shared a similar concept: The (mis)adventures of the crew of a bustling space station. The divergence from there is extreme.
DS9 very quickly brought in the Defiant so that its characters could escape the station and go on more traditional Star Trek adventures. The station was home base, but the crew got out a lot. It typically felt like the station was well under control, with only minor differences between it and a star-fleet vessel. (Toss Quark and Garak out an airlock and you'd pretty much have a standard starship.)
B5 did send its characters on excursions, but they were fewer and far between. The station was not a safe home base. It was a bigger and wilder place than DS9 ever was. It always felt like some crisis or another was ready to spiral out of control and the staff generally needed all hands on deck to deal with whatever was happening. DS9 had the occasional crowd scene, but B5 had bigger crowds (in record shattering amounts of alien makeup) every episode. DS9 felt like a sleepy frontier fort. B5 felt like a city.
Then there's the continuity. There just wasn't a lot of continuity in anything other than soap operas in the mid 90's. TNG occasionally had multi-part episodes and sometimes referenced earlier episodes, but it was always careful to explain things so you could jump in anywhere and not be lost. DS9 was initially episodic, but had some larger arcs in later seasons, perhaps as a response to what B5 was doing. B5 broke the mold. The first season seemed episodic at first glance, but each episode advanced the central story-line. You could jump into Season 1 at any point and be a little confused, but figure things out. That swiftly changed. Later seasons became completely continuous, and frequently relied on bits of story that happened in earlier seasons without any kind of hand-holding. This caused big problems that probably prevented B5 from being as well received as it should have been.
This is for the young whippersnappers out there who grew up with the internet, streaming, and home video: Today, if you decide to jump into a show, you can call up every episode on demand. If it's not on a streaming service, it's on DVD or VHS. Failing that, there's always piracy. When B5 came out, it was not a given that a TV series would be released on VHS or DVD. The internet was there, but it wasn't yet up to distributing video. There was no such thing as streaming. The era of Netflix mailing you physical discs was years in the future. If you wanted to watch a TV show, you had to tune in when it was broadcast. It was, essentially, live TV.
The kicker is that most broadcasters were utterly irresponsible in how they aired shows. Episodes would frequently be pre-empted or aired out of order. Broadcasters were used to purely episodic content. Who cared if people saw episode 5 before episode 2, or missed episode 3 until it got reran the following year? This royally fubar'd people's ability to follow B5. My personal memory of B5 when it first aired was fragmentary and frustrating. I'd watch an episode and really enjoy it, try to tune in next week only for it to be pre-empted by golf, and then be lost when an episode from much later in the season was aired the week after that. It wasn't until B5 came out on DVD (years later) that I was finally able to watch the show in order and finally appreciate how special it was.
Continuity between episodes is normal now. Everyone is used to shows that play out as one long narrative instead of hitting the reset button every week. B5 blazed the trail for them before TV distribution was really ready for continuity. There are a lot of warts to overlook. CG was in its infancy back then. DS9 was still using physical models in its first few seasons. B5 looks like it came out of somebody's Amiga because it literally came out of somebody's Amiga. There probably won't ever be a quality up-scaling of the special effects because a lot of the files from that Amiga were lost. The set design is clever, but stagy. The budget of B5 doesn't even add up to half a shoestring by modern standards for a show with 10 episodes a season, and B5 had 22 episodes a season! The story is so grand and detailed that it still feels rushed at times. (They thought the show would be cancelled at the end of S4, so they crammed most of S5's plot into S4. The result is fantastically dense and frenetic!)
In the end, DS9 was a fantastic show but felt a lot like the station featured in it. It was always well under control and its creators got everything they needed to deliver a compelling show. They knew how far to reach and chose their battles wisely. B5 feels like a wild and overreaching fever dream by comparison. It nearly span out of control, much like its titular station was always threatening to. If they decided to re-make B5 today, they'd probably simplify it immensely. It's story still seems too ambitious for a single TV series to tell. If you can get past the warts, B5 is still a unique and rewarding series to experience. Nothing quite like it has come along since.