Greening Labs did extensive testing of brake rotors in general for the US Postal Service.  The tests included a lot more than just wear, they went through a whole battery of tests.  The brake that did the best was a cryo treated brake which is now specified by USPS.  It got seven times the life of the second place brake which was a Brembo brake.  This was an unbiased test by a nationally recognized independent laboratory.

I realize that there is a difference between police use and delivery use, but our racing experience indicates that cryo treated brakes hold up under the heaviest high speed work also. Porsche has been using cryo treated rotors on their endurance race cars for years to avoid rotor changes in 24 hour races.  Yes, these are lighter cars than the typical police vehicle, but they are used at considerably higher speeds and for considerably longer chases. 

Another note.  Recent calculations show that there is a definite energy savings in the use of cryo treated rotors.  Recycling of rotors requires they be melted down.  The melting of the rotors is energy intensive.  The use of a cryo treated rotor amounts to saving approximately 100,000 BTU's per rotor over the life of the rotor. 

Also of environmental interest, brake pads tend to last longer when used against a cryo treated rotor.  Brake pad wear is a major source of copper pollution that affects marine life in coastal areas.