Alright, I bought an X50 last month and have been getting accustomed to it, and found it to to the job well. My dad decides maybe he should get a radar detector, and picks up an Original 8500 off of ebay for like $180 shipped (Detector, SmartCord, and Windshield Mount only, no box/instructions).
I put both in my window and ran back and forth each of the known radar sources (falses).
Both detectors reset to factory defaults (X50: Rev 5, 8500: Rev 15), then changed to Expert Meter (all other settings left factory). Mode for both is Highway (for maximum detection, even in the city, this is a test of range not falses yet).
He was concerned maybe he'd have bought a lemon and wanted me to test his to make sure he could leave positive feedback. X50 mounted on left 6" from dead center of windshield, original 8500 mounted on right 6" from dead center of windshield (1' of seperation). Both detectors cycled multiple times and no errors come up (a good sign, but lets test range already).
Okay, I drive by my local Shop-Rite, and they have two X-band door openers that peak at about 4/9 in highway mode, and as I round the corner both detectors nail it at seemingly the same time. As i pass by (store on left) they both track each signal properly, and as I pass by they seem to drop off X at the same time. I turn around to make sure the results are repeatable and that there arent any differences with either being closer/further away. As I pass the church and get my own first glimse of the building both detectors go off once again at what seems like the same time, and as I pass and go around the corner hang onto the X band for the same amount of time.
Verdict: X band? Seems Identical.
Next I test my K at a known K false at my local shopping mall. As I round the corner into the shopping center I get a weak K on my X50 and the 8500 stays silent. Then both are silent for a moment. Seconds later as I begin to pass, unfortunately both detectors reset when I hit a pothole that jolted my 3-way lighter adaptor loose (its a heavy *****, it is now in the garbage). When both snapped back to life after POST, both picked up the K immediately, and as I passed the building the X50 hung onto the signal longer with it in my rear.
I go into the mall, and purchase this Y adaptor which has alot more give (wires instead of a solid brick thing that looks like this which is GARBAGE.)
Okay, I come back out of the mall and there is maybe 1/4 mile of parking lot between where I parked (near radioshack) and the false (borders?). As I approach the building @ 15mph from a distance, the X50 nails the signal many seconds before the 8500. The 8500 doesnt get the K band until much closer, and as I pass the building they both seem to peak at about the same place, and as I drive away from the building (to my right side), once again the X50 stays locked onto the K signal for a longer period of time.
Verdict: K band? X50.
Unfortunately I cannot test KA or Laser because I have neither seen them on the highway yet, nor found a reliable stationary false signal to test them with. When I do, I will test them head-to-head.
Keep in mind this is fairly non-scientific beacause I did not have "feet" or "mile" measurements, just eyeballing this over the period of about an hour of work. I made two passes each test, once with the source on my left, once with it on my right, perhaps multiple passes each way would have better confirmed my results. If anyone can directly compare the 8500 and X50 in laser or KA, feel free to add to this.
Thanks for reading!
PS: Whats the latest firmware rev. for the original 8500? Or the latest known firmware?