I believe a key concept in differentiating between traditional and modern quilts is repetition. Are you making the same unit 354 times? If so, it's probably safe to identify that as a traditional quilt.
Modern quilts are less repetitive in design and tend to use larger pieces, with fabric of brighter color and wilder texture, lots of white and empty space.
But in the end, I do think it's a case of 'know it when you see it.'