The more I watch DS9 the more similarities I do see between it and B5 to think several of the concepts were a ripoff. It is different enough though that I can still enjoy it. In fact it seems that DS9 "tries" to have a cohesive story like B5 did, but didn't quite pull it off. Even without the true story arc they do a very good job at telling lots of shorter stories and I do also think it is the best of Trek series. Garak's charater IMO far outshines anyone in DS9.(I know DS9 many claim was ripped off of B5. O.K. so I even think it probably was. It was still the best of Trek.
Heck, the more I watch the Lord of the Rings trilogy, I also start to see where people could argue that lots of B5 concepts were taken from the LOTR. I never thought so before, but after watching the trilogy...I hate to admit it, but I see it.