I consider DS9 as the best Trek show (yes.. even better than TNG or TOS!
) and with B5 you get the same level of amazing characters and a huge storyline that gets built up slowly but steadily.
Back when it was originally aired i was glued to my seat as a teenager and luckily the internet was still in its infancy so the chance of being spoilered was quite low.
Personally i think most DS9 actors were better than the ones in B5 but the character arcs of Londo Mollari and G'Kar that span the entirety of B5 are just epic.
If you liked DS9 you will definitely enjoy B5.. get past season 1, the occasional bad filler episode and the outdated CGI scenes and enjoy the story.