Does it do the same thing that the ones that spin around with the 2 blades?
Is one better then the other?
I know nothing about radar.
Well, all things be equal. No, its not better. What I mean is, an open array that is 20 years old. The Simrad that I have, could be better.
The open array is what you are talking about. Those will give you more power and better target separation. Every radar has a beam that it sends out. That beam, as in the open arrays could be 1 to 3 degrees wide. The model I have is 4 degrees wide, so it could see 2 buoys as one depending on distance. When I say 2 buoys, I mean the red and the green at the same gate. Which is less likely with an open array. Which is target separation. The other is power, but you have the earth's curve so you may want to mount it higher for distance. That power will help in distance and though bad weather which will cut your range down.
Though may boating years, I have been in fog a few times. My first 2 boats did not have radar and it was nerve racking in fog!! Years ago the wife and I went to the N.E. Boat show. We walked by a display with radar domes. The short of it, she bought one! She said never again, I am buying it.
Like the saying goes, I want leave home without it.