I can provide some insight. I had hardwired a radar detector in my car and noticed the range was not so great. I thought it was all the coatings etc... My radar detector was about 7 years old. I saw one on sale and decided to upgrade.
What a difference! I think the sensors were losing sensitivity on my old unit and it was the reason for shorter range. My new one gets 2-3 miles in my tesla.
I had been debating getting one of those hardwired front of the hood kits. With the performance im getting now, its no longer needed.