Minolta AF 300mm/4 APO or Tamron 70-200 2.8 ?

I've been looking for a birding-lens, and have found these used lenses in my local area so far.

I'm going to use it outdoor, in good light, preferably with a x2-TC (which I still have to find).

I can get the Tamron for about half-price (compared to the price of new lens in store), and Minolta would cost me about 40% more (almost the same as a new Tamron in store). Both are mint and little used, according to the sellers. Which one would you guys recommend? Or maybe there is a better alternative for a birding-lens in the price range?