My first big impression of this test, is that I prefer the distortion of the Fish eye for this angle of view. The Tamron is really good to maintain rectilinear structure in many picture, but for this one, the view look more realistic with the Fish eye.
On first view, the detail of Zenitar looks good up to F5.6 to F11. At F2.8 there is flare and lost of detail. But not bad for the price.
The big difference I have seen with the Tamron, is that the lens need at least half a stop more light to give the same histogram. The Zenitar was at full aperture a little bit brighter than the Minolta, but up to F/4.0 It was difficult to see a difference.
Probably more viewer will discover other differences

.
Budget wise, and for outdoor usage at F/4.0 and up, the Zenitar is the best choice I think. But for low light, nothing I think can beat the Minolta.
Regards,
Frank