well...I could write for days on this issue (where to mount the
radar detector).
To keep it quick and simple...
LASER--if you live and drive in an area where the officers use mostly lasers to track your speed...you want it as low as you can get it without it being blocked by wipers...ect. Normally, the officer will shoot the laser at your front tag/grill/bumper. Laser speed detection is instantaneous. You will be ticketed before you even have time to hit your brakes!
KA, K, and X band use the waveguide inside the detector. Think of the waveguide as a funnel. You can pour a ton of oil in it and not worry about it splattering all over the place...similarly, you can pour a massive KA band out and the funnel (waveguide) will catch it...practically regardless of where you mount it in the front you will be alerted in great time with a quality product.
I have the Beltronics Pro RX65, simply amazing! 5 years old and refurbed on ebay and still works incredibly well!
On I-65 in Alabama, practically flat terrain, I can smell the heat from 3 miles away on a clear day!