As far as quality, Northstar and Furuno take top honors, but that does not mean they are the easiest to use. Garmin is the absolute easiest to use for most people and they have a good product, Raymarine has good products too who are not far behind in ease of use. Raymarine had a lot of issues with there multi units having screens fog up and with software issues, they claim to have fixed it on newer releases but I still hear of issues, just not as many, I think mounting location and angle have a LOT to do with this current issue. Northstar makes the BEST quality gps/chartplotters but they are not the simplest to use, but they are reliable and very accurate. Furuno makes great products that are reliable and offer top quality for all components. Furuno has high quality radars, FF and plotters, Garmin is best known for plotters, there Radars have come a long way and become very good, there FF are decent, but I have not seen them to be as accurate as furuno or Raymarine's as of yet, but they are getting close. Raymarine makes an awesome radar, FF and plotter, but the above mentioned issues make me leary to spend that sort of money on a multiunit from them.
Personally I run Furuno electronics, they are commercial grade and last, I've never had issues with them and they are reliable and accurate.
Working for many high end boat builders, I've seen a lot of electronics on boats, but most owners who spent high dollars went with Furuno, a handfull with Simrad, a very small number with Raymarine, and then Northstar or Garmin were typically used as either the primary or backup GPS/chartplotter. A lot of high end tournament sportfishermen left with Northstar for the quality and accuracy, a lot of owners who operate there own boats or who cruised more went with Garmins for ease of use. Things are different when your spending $40-50k on electronics or more, but these owners all picked electronics that suited there needs the best. whatever you buy needs to be something you can use, something high end reliable and accurate may be something you cannot operate, and then becomes useless, so take a peak at electronics at an expo or boat show or a local shop and have someone go over them with you and see what your comfortable with.
Personally I'm not a fan of multi units actually, I hate splitting a screen, but on some boats its all there is room for. I prefer a separate FF with a dedicated screen. The only reason for a multi unit is to put radar overlay onto a gps/plotter which comes in very handy and makes navigating a lot easier and safer. On multiunits, if one unit goes, they ALL go, making repairs and fixes more expensive and more likely down the road, with separate units, one might last longer then others and not warrant a replacement. Typically FF do not change that much in technology, the only new trend coming our way is multi frequency units where you can find tune the frequency to target your targeted species for that trip to more accurately locate fish, gps and radars are constantly updating and evolving to be more accurate, show more detail and come out with better technology. These units are going to more then likely need to be replaced a lot sooner. Not saying this is best for all, but take that into consideration before you spend a lot of money on a new unit, see what suits your needs best now as well as 5 years from now.