Actually, it depends how much searching Show has to do. When every brainstorm, ponder and preordain cost a mana more, it's hard to cast two in the same turn, while you can easily drop two Elves. Actually, it's sort of best at the turn they'd want to S&T, cause then suddenly they don't have enough mana to cast it and sometimes have to pass the turn and you hoof them in that turn, since you're cradle taps for a zillion mana anyhow.
Sure, if Show has the nut draw, it doesn't matter that much. The chances of winning while Thorn is on the board become significantly less though. Please remark this is why Goblins side in Thalia vs Show.