They both have strengths and weaknesses. The Infinity Modulus system has the better high end by far, and the transient response is awesome. You will hear details that elude other systems. However, vocals can sound somewhat nasal, and there is no bass (upper or lower) to speak of. The Paradigms will reproduce these areas better.
HOWEVER, if you combine the Modulus satellites with their dedicated crossover and subwoofer, a totally different picture emerges, with a cohesive sound from top to bottom (although somewhat lacking in the deepest bass and dynamics compared to today's better subwoofers). Bottom line: if you're going to use a subwoofer, get the Infinitys. Otherwise, sonically and budgetwise, you're better off with the Paradigms.
Final note: if you're talking about the Paradigm ACTIVE 20's, throw all the preceding out the window, and buy those.