Tire Streets sells three different PHI tires, the Accelera PHI, the PHI 2, and the PHI R. But how do they differ?

The trilogy of PHI tires is great for street driving, canyon runs, in almost any condition. Do you want to be able to perform on a track in either drift or racing situations? Do you have a low HP car (anything less than 400hp)? The PHI tires will give you that opportunity without breaking the bank.

They are both are produced by Accelera, and both are performance tires. So, what are the main differences between the Accelera 651 Sport and the Accelera PHI?