As I've said before, I don't like to compare the two shows due to their vastly different writing approaches.
Both have great arcs overall (and both have some stumbles along the way). B5 is an example of how a show can be brought to life with a great deal of pre-planning and forethought. DS9, on the other hand, is a great example of how a show can achieve great things even while the writers are, to some extent, flying by the seat of their pants.
I guess we'll never really know how much the two may have influenced each other, but for my money, both are worth rewatching. That said, if I'm forced to pick sides, I will say I think early DS9 flows a bit better (if more episodically) for me than early B5, and the Sinclair-Sheridan swapout while other casting changes are underway is a bit jarring even if one feels that Sheridan is ultimately better suited for what's to come.