No other unit on the market has the screen resolution of the 700 series units. BUT with the Side Imaging technology, screen width is most desired whether it is the 800, 900, or 1100 series.
Larger screens display stuff larger even though the resolution (pixels per square inch) is less.
The screen size is not all that important for regular sonar or Down Imaging since the display scrolls from right to left and is based on depth. The Side Imaging scrolls from top to bottom and you choose how much range to display on each side. That is where screen width becomes important since that deternines how large returns are displayed.
I have the 798ci SI and a couple of 1198c SI units. The 798 is OK for a console application, but a larger display is better at the bow since the unit is farther away from you and small details are hard to see from a distance. That will be very apparent as you get older.
Additionally if multiple views are displayed, the larger screens are better.