The only real difference any inland user will see is screen size.
Think about your application: will you be trying to see details (particularly in SI) from a distance? If so, do yourself a favor and buy the 998.
Will you be using the unit mostly while seated directly in front of it, and not trying to use it from a distance? If so, then the 898 will probably work just fine.
I spend more than half of my time pulling baits from the transom with a console-mounted unit. That means I’m trying to use my graph from ~6 feet away. I had a hard time seeing small details in SI (particularly under typical fishing conditions….wind, waves, spray, glare, etc etc etc) on my 997, so I upgraded to the 1197 which solved my visibility problems completely.