A while back I was looking for the perfect goose gun - I found the Browning Gold 10 (10ga. semi). But then I backed out after deciding I did not want to defeather, gut, clean, etc. a bunch of birds.
For geese I would always prefer a 10 gauge - if someone says "my 3.5" 12ga load is close to if not as good as a 10ga", they just admitted that a 10ga is the gold standard to which everything else is measured.
In my books a semi auto will always beat a pump action; obviously it is faster (I don't care how quick you are with a pump it is still faster, even if only a little), and the semi automatic action seems to dampen the felt recoil. As for reliability, I have had more trouble with a Remington 870 than any semi automatic firearm - but even if semi autos are slightly more prone to mechanical failure, would it really matter if at sometime during your life you have a malfunction, need to recycle the action, and it results in you missing a goose?
I could never understand why someone would subject themselves to the torture of a side by side or over under; you add twice the barrel bulk and limit your magazine capacity.
But I know that everyone has their own ideas and preferences, and I don't try to convert anyone to my way of thinking. As you may have guessed I am all about the modern and hold no value in 'tradition'.