I'm in the market for a new ej257 block for my 04 STi and I am wondering if it is worth the extra thousand dollars to go with the closed deck or if I would be fine with the open deck?
You have to tell us what you are trying to do for us to tell you if its worth it. But yes you should, because closed decking is done in America and supports our economy.
Like the others pointed out, it truly depends on what you plan to achieve with the short block so if you'll give us an idea of what power level you're after then I can make some recommendations for you; but yes, in general 600+ will require some sort of block reinforcement (whether it be pinned or a closed deck).