The main thing to focus on is make sure you get a high quality laser radar detector form a manufacturer like: Whistler, Beltronics, or Escort. Ka is the most common frequency used 90% of the time by police. When choosing a radar detector, make sure you get one with 360 degrees detection from all bands: X, K, Ka, Laser, POP, and Pulse. Ku is a European band and is not used in the USA. POP and Pulse are modes that police use to send quick signals that might not be detectable by cordless or older radar detectors.
Some cool features are a compass, dark mode, or radar detector invisibility from spectra or VG-2 (for use in states where radar detectors are illegal). Some of the new radar detectors have GPS that come pre-programmed with the locations of red light cameras, which is cool, but this feature can add to the cost of your product and you have to pay monthly to update the list.
Escort is know as the manufacturer whose radar detectors have the longest range and early detection. The new Redline has the longest range, while the 9500 series has a ton of features such as red light camera database, low false alarms, and a learn feature.
