One other thing worth mentioning. The HDS I have is very slow when you toggle back and forth between the fish finder page and GPS page. Not a huge deal breaker but my Raymarine is much faster just push the button and you are there. My HDS takes a while to find location when I fire it up usually a 3-4 minutes where as my Raymarine is less than 20 seconds. Maybe because the antenna is built in to the HDS and its under a T-top and Raymarine is separate but it does take a while to load on my boat.
The toggle back and forth being slow drives me crazy though. Most of the time I use one on GPS and the other on finder but when I was in FL about a month ago I loaded a map in my Raymarine that was the wrong file and it messed up my gps had to do a reset. But I couldn't do that until I got home because I did not have a card to dump waypoints on with me. Anyways resulted in me using my GPS only on HDS and finder on Ray which is opposite of my norm and it was very slow to zoom in and out or to switch pages from side scan to gps. Drove me crazy all weekend, if I was used to that maybe not a big deal but since I was not it was very aggravating. Not sure if an HB is any faster or not to toggle back and forth but that would be one more thing to consider. Not only back and forth but zooming in and out is slow as well.
As DUAYNE mentioned, the down scan works really well for separating fish and baitfish the image is different that of 2D so you have to look at it different but it is very refined in separating the two. The two things I use this most for is the down scan and side scan. Side scan to find fish then structure scan to determine what it is or isn't.