Lowrance is the most user friendly IMO very very easy to read and set up. Also believe they are the easiest to read and portray walleye "hooks" the best. I would also go color, you can mark fish on plane at 25 mph, can't do that will monochrome.
Garmin, Hummingbird, Raymarine also make very good units too. Keep in mind the power of these units, for Erie you want something with 500 watts RMS.
You need to give a price range when you talk about picking out electronics to get an accurate response. Units can range from $150 to $2000 each-so alot depends on "whatever you can afford" as the old saying goes. I recently saw a Lowrance 520c and was pretty impressed, especially for something costing less than $800. The 111/112/113 Lowrances are sweet as are the 26/27, but more $$. IMO the best I've seen is Raymarines "C" series. You are talking quite a bit more $$, especially if you get standalone GPS and finders. Most importantly, the unit is only as good as the transducer installation. Get a shoot-thru or thru-hull transducer if you want a quality reading at speeds.
Love my Eagle fishmark 480. $200 @ Gander. 5 inch screen,480 x480 resolution, has FishReveal, grayscale, reverse grayscale. I'm sure the same readings in color would be better, but for monochrome, I love it.