One of my favorite vessels in Star Trek series is "USS Defiant"!
The big difference between Defiant Class ships and other USS Space vessels is it's purpose.
Many USS Space vessels were built for "Quest" but Defiant class ships were built as "War ship".
The first and second season of Star Trek Deep Space 9 was a kind of "Detective Stories" like as Sherlock Holmes for me.
Crews solve mysteries and cases in limited space in the large space station or just short space trips by a lunaboat.
But from 3rd season, crews had to go out from the station and deal with threat.
Federation provided a new model ship for Deep Space 9.
It was "Defiant".
Defiant participated in stories actively from Season 3 to 7.
However, Defiant was destroyed in fleet war in Season 7.
Captain Benjamin Sisko was given another Defiant Class ship after he lost his vessels.
It was "San Paulo".
Captain Sisko was given a permission to change the name to "Defiant" at the discretion of the Federation.
Here' s a way to distinguish old Defiant and new Defiant.
Below are pictures of Captain seat of old Defiant.
The leg of Captain panel has curved legs.
And....here's the picture of Captain seat of new Defiant.
The legs don't have curves, it' straight stand.
Well... I'm SiFi geek!