I've owned them both on the same rims.
I concur with ryder1 that the Fatti-O have a protruding edge where the tread meets the sidewall, making the 'wider' at that point. The Thick Brick has a more 'rounded' profile and smoother transition from sidewall to tread. This is probably why the Felts have SUBSTANTIALLY thicker sidewalls than the Electras.
Go for the Felts, they're a quality tire.
Cheers,
Dr. T