That's all a matter of personal opinion as what you may consider "hardly notable" might be glaring to someone else. Someone may consider the stock ships fine as they care about the gameplay more than what the Enterprise looks like. However, others who do care about the quality of the ships would want them to be as detailed and accurate as possible. Some of us get that by texturing in the details, others of us get that by modeling it in, and still others find the right balance with both. Either way is a personal choice and depends on just how much effort we think each ship deserves. Whether or not the users out there notice such differences depends on the individual's preferences and their bias regarding a particular ship.
If the game couldn't handle a 5000 poly B'rel or 9000 poly Ambassador, then nobody would build them at that level. KA, Freelancer, Armada and other games have a limit on the polygon count vs gameplay stability and the modders for those games work around that. SFC isn't quite so restrictive and the game engine isn't as weak as some may think. The deciding factor is the user's computer power, not the game - I myself have been able to run a half dozen hi-res ships at one time without any lapse in gameplay.
No modeler is going to limit themselves to a 3000 polygon cap if they feel their ship needs more and especially if it's a canon ship that requires an extra kick. Textures have their limits and many times, they just don't look good enough in place of modeled detailing - which is, also, a matter of personal opinion.
Anyway, to answer your original question, I don't recall ever seeing a TrekMods B'rel posted for SFC but I remember seeing images of one. If it was ever released, I'm sure one of the ship fanatics around here are bound to have it.