Oh come on.. give it a rest.
There were similarities, that's certain. But they are superficial and the main stories diverge extremely because they have a totally different focus and style to them. The characters are also very different.. yes, Sisko has lost his wife too, so what? It's an age old tool to give a character a chip on his shoulder, a background and some drama (especially if the wife died violently and the character meets the killer at some point). B5 didn't invent that, DS9 didn't and it has been used since boths shows started.. you don't see other people get up in arms when those shows aired crying "But my show's main character also has a dead wife/husband/relative!!!"
I fear however that given the people in fandom that this topic will never be settled because some people can't let stuff go, much less the creator of B5 (for whatever reason.. he created a brilliant story and people talk about his show nearly 20 years after it concluded and that's not bad).
I prefer B5 for its overal story which had me glued to the screen much more than DS9 but then again DS9 had the far more rounded characters and better played by the actors (with the exception of Mollari/G'Kar who are both the coolest duo ever in SF and were played to perfection by Jurasik/Katsulas).
So why don't we enjoy both shows equally for what they were.. flawed at times but providing excellent SF entertainment.