How much range do you need to see what's in front of you?
That's a real good point for potential radar purchasers to keep in mind. The requirements for a blue water cruiser are going to be different from the requirements of a coastal cruiser. And in the coastal cruiser category the requirements are going to be different for someone cruising in the maze of islands and channels that make up the PNW, BC, and SE Alaska coasts and (I imagine, having never done it) someone cruising long waterways like the ICW.
Here in the PNW, the straight-line range to an obstacle like an island or the mainland is rarely more than three to five miles other than on the larger bodies of water like the Strait of Georgia, Queen Charlotte Strait, and so on.
Our Furuno NavNet VX2 with a 24" antenna has a theoretical range of 36 miles (IIRC). But what we're really interested in is its sensitivity, return clarity and target separation from 0.125 to 3 miles.
The longest range I can ever recall setting the display to is six miles and that was more to see what it looked like than to actually use it. Sun or fog, we are always running at three miles or less. In the very narrow passes we go though, sometimes in dense fog, we'll be at 0.125, 0.250 or 0.50 so we can see crab trap floats, little sportfish boats, etc.
We would have purchased our NavNet with a 36" antenna if it would have fit on the mount. Not because we care about seeing any farther but for the increased target separation and clarity. But we've found our 24" antenna does fine for us.
Our antenna is also mounted fairly low. Not a problem for us since we don't need to see long distances, and it's an advantage in seeing small things on the water right up to the boat. If we were open water boaters, however or were boating long, straigh-ish waterways where seeing what was coming at us or up behind us while it was still some distance away, a low mount like our would not be beneficial at all.
So, like almost everything else to do with boating, there is no one-size-fits-all solution when it comes to what radar antenna and radar power is best for each boat.