I've listened to several of Fiddlershop's Master Concert violins, and color me impressed. Most violins in this price range are usually very bright, with average-to-below-average response. Fiddlershop's Master Concert violins are a welcome change. The violin's tone is warm and even across all strings, which is just rare in at this price. Not only that, but even when Fiddlerman plays very high up on the G and D strings, the violindoesn't choke (some violins that cost thousands even do this).
I know nothing of the Yamaha, though it's hard to imagine their instruments being superior. You could try out both (get the Yamaha first, so you don't have to ship back the Fiddlerman Concert violin, because you'll most likely keep it ;))