On my 330 i had a set of E120's and was very happy. On this boat i have a set of 4212(same as 5212 but not touch) and i'm also very happy. The two main differences between the two (my opinion), i really like the navigation on the Garmin and is very easy to work with, and i really like the Garmin HD radar, what i really wish i had is the Raymarine sounder, in my opinion is the best sounder tied with Furuno. If i would do it again, it would be sounder on a E120 and everything else Garmin. This way if one of the GPS goes, you always have the other. What is good about Garmin is that you don't need a split screen to have radar overlay. Good luck and let us know what you pick.
P.S, i also have a Simrad AP28 auto pilot, which is a great unit.