It depends for what you want the Radar and how much you are willing to pay for.
I have a Fantom 18 and it does its job, but the new
GMR xHD3 seems to be considerable better and in case you want the best then a open array will be better than a radome, but much more expensive.
As LuckyDude already mentioned, the radar should point in the correct direction at the speed / boat level the radar is needed and that is usually pointed down a bit to compensate for bow high at low speed/no wake zone to see near objects in front of boat.
Chris