Controversial Opinion: I both love and hate the Defiant.
On one hand, it's an absolute cool and badass little ship. I love the idea of a little ship so overpowered, it almost tears itself apart. It did it's job, and then some, in the Dominion war and was exactly what DS9 needed at the time.
That said....
I hate what it represents, a glorification of war. When someone says it's their favourite ship, I almost get sad. Starfleet is an organization of exploration that also happens to be able to defend itself. Their ships are instruments of science. What the Defiant represents, kinda goes against everything Starfleet stands for.
I get it, between the Romulans, the Borg, the Dominion, etc. Starfleet was most definitely feeling the pressure and the Defiant became a necessary evil for a more hostile Galactic landscape.
I almost wish we didn't see the Defiant at the Starfleet Museum. Being that it was essentially the personification of Starfleet at war, I would think it wouldn't be something to be glorified.
But that's me.