I've tried both black and white truffles on separate occasions, but never side by side. Is there a meaningful difference between the two as far as flavor is concerned?
Yes, yes there is.
Black truffles are dark, earthy, sexy in flavour. Renaissance writings compare them to 'unwashed slatterns' and 'bedchambers, rooms of sexual congress, unaired and reeking of the recent activities contained therein.'
White truffles are lighter in aroma and flavour, with distinct garlicky notes. Each has their place--black works better on its own, white works better as an adjunt or finishing note to a dish. I am personally partial to white truffle oil drizzled on cured duck breast, or a black truffle risotto with charred endive.