While I don't own a 3" Unitron, I do own a 60mm 114 Unitron. I also own both 80mm f/15 and 102mm f/15 Celestron/Vixen refractors. I've taken many opportunities to compare the optical qualities of each scope with my 3.5" Questar Standard, and they all seem to perform as expected for what they are. In my opinion, they all exhibit extremely excellent optical performance, but each in their own way. When used independently, they all seem to be pretty much free of any false color. When compared with the Questar, however, the Unitron seems to lean ever so slightly toward the yellow end of the color spectrum, while the Vixens seem to lean ever so slightly toward the blue (which somehow I find to be more pleasant). As for optical performance, when conditions allow, I can increase magnification on every scope to the point where the image is almost too dim to see and the images don't seem to break down.
Still, larger optics of equal quality will show more fine detail. They also gather more light for a brighter image. When comparing my 80mm Vixen refractor to my Questar, the Questar goes a little deeper and shows a bit more detail. As an example, I had both out looking at Saturn a few days ago and although both displayed images were similar, I had to use my Questar to confirm the placement of a couple of moons that I thought I was seeing with the refractor. On the other hand, the double-double, Epsilon Lyrae, always looks to be a little nicer and more pristine in a refractor due to the almost complete lack of the first diffraction ring that is quite evident in a Maksutov.
As for my 102mm refractor, it's in a class all its own and not a fair comparison to any of these others. Still, at 125 to 150 lbs, along with many trips required to set up, it doesn't see nearly the amount of sky-time as the rest (the Questar wins hands-down in this respect).