The first GranaryA you play in a turn is just the same as a warehouse. It's more stackable, and it's better against discard attacks, etc. But worse against Governor/Council room.
Just because it's more different from Warehouse, I like B better.
Oh, man. I strongly disagree. Is Type-A often similar to Warehouse? Yes. Does being quite similar to an existing card make it less appealing? Yes. But all other factors I can think of come out in Type-A's favor.
First,
Type-A is better against discard attacks. If you have 4 or fewer cards in hand before you play it, Type-B is just a cheap Laboratory. Don't get me wrong, Lab is a decent anti-discard card, but in this case, the Draw 3/Discard 1 effect becomes more interesting. If you play them with 3 cards in hand, they both leave you with 4 cards, but Type-A gives you a bigger selection. You could say that Type-A is more
indifferent to discard attacks, and I like that. Granted, if you have two copies of Type-B, you come out ahead, but that brings me to my next point.
You need fewer copies of Type-A to get a bigger effect. Because it costs 4, it's not too tough to load up on copies of Granary, but with Type-A, you need fewer copies to get the benefit it offers. Type-B offers a bigger potential benefit, but you need more copies of the card to achieve it. With Type-A, I have more buys to spare on other cards.