Though I enjoy fiddling around with Gremak designs the most, my favorite individual style is the Terros Ligth Cruiser
in the below configuration (with disruptor guns and a round PD turret on the top)
This is not considering small crafts where Human bombers win by a landslide
The design reminds me strongly on Wing Commander Prophecy and always looking for a way to update it in a way that I can keep using them in my games
Besides the nostalgia factor, it also has an aura of authentictiy to it: the ship looks like it might actually be able to fly in atmospheric conditions as well (though probalby not, it does remind me of a Black Bird), which might actually be expected from a small cruiser especially since it does not require a space contruction module. The same cannot be said from the Ashdar Destroyer, which while a sleek design, I have a harder time emagining to be flying around and leaving the atmosphere. This is probably why I like the idea of the smallest ships (not requiring construction module) to deviate from the larger ships in style and be more sleek and aerodynamic.
My least favorite has to be the Tinker Destroyer
and the reason is quite simple: most races have a distinct difference between their destroyer and all of their other designs that follow a common theme. I find the Tinkers to a be an exception of this where it seems that the overall design theme (especially the light cruiser) has influenced much more heavy the Destroyer design where I find it doesn't work. While the concept for the race is clear I wish it was a bit more sleek design like a Cylon Raider but the additional widening around the sphere just doesn't work for me
To be clear: I do enjoy the larger Tinker models a lot especially the Light and Heavy Cruiser designs around which I think all other Tinker ships were designed