>>95964697
Shadow is likely the stronger card overall, but Sonic is a much better value engine. Red is stuffed with group symmetrical damage dealing spells, so even assuming you never attack with Sonic, his 4 toughness survives most of those while giving you treasures. Pyrohemia alone lets you shit out at least 3 treasures a turn cycle, and if you use Unwinding Clock, which is already good in an artifact heavy deck, you can maintain this burn in every turn cycle. Hell go nuts and mix in Ghirapur Aether Grid and just have your Treasures ping Sonic.