You should ask yourself whether you're in for the long haul with Sony and whether you're going to go full frame in future. If yes then the Zeiss will be a much better investment. The 28-75mm is strictly for those with a FF cam and tight budget.

ahpingko : That depends on the condition of the lens. As you already know the beercan is an old lens. Although it's built like a tank but wear and tear do occur over time so make sure the lens is in good condition. The beercan is also a slow focusing lens although the 75-300mm is not fast by any means but keep that in mind. Of course if you like the 'Minolta' look the beercan is famous for then it's a good buy.

ieR : I like the shot but one thing bothers me. The grass flowers (the white bits on top) is much brighter than the subject and I feel that it is a little distracting in a sense. That's just me lar... nice shot overall.

Erm depending on what you mean....

If you'd know you are going full frame, might as well prepare towards FF rather than buying DT/Aps-c lens and selling em off later right?
No rules saying for pros only, but FF does bring an illusion that one's somehow

Ehem, never mind. Scrape that topic.