They're the Federation's neighbours - methinks they'res going to be some technology leakage, despite Starfleet's best efforts. The ATR-4107 Missile O' Doom was equipped with quantam torpedoes - a recent development as of the late 2360s/early 2370s. I see their ships as being technically roughly on par with Starfleet vessels - but I don't think the Cardassians have ships as big and powerful as the Galaxy-Class etc. - which is why all the confrontations in TNG were like "STFU or we'll pwn u, stupid spnheds, lol". I think they have less resources than the Federation and basically have to make do with smaller, more single-purpose designs. I see Cardassia's starfleet as far smaller and more specialized than the Federation Starfleet - masters of making lemonade out of lemons, if you will forgive the Earthcentric metaphor.