What's the difference between Normal and Polish routes?
There are no significant differences in technical difficulty between both routes.
The 360 Polish Glacier Traverse route (17+2 days), also called Two Faces or False Polish route, is much less traveled, with better views. As it takes more days to arrive at Base Camp, the acclimatization is more gradual, but it is a little colder, and as it is longer, it takes more time and energy to arrive at Base Camp Plaza Argentina. Through 360 Polish, you will know the Tow Faces of Mt. Aconcagua.
The Normal route is a little easier, offering in a certain way more possibilities to reach the summit, especially in the Extended itinerary (18+2 days). Still, it is not a big difference anyway. This option also offers the opportunity to reach 2 summits instead of one: Mt. Bonete (16702ft/5091m) + Mt.Aconcagua (22834ft/6962m).
The Normal route also allows a Fast Ascent (14+2 days) or Extreme Ascent (12+2 days) for well-trained and acclimatized climbers who want a challenging program.
See also
What's the difference between extended and fast/extreme itineraries?