How much do you rely on electronics? What is your intensions for aquiring a unit? What type of fishing do you do? All questions you have to ask yourself.....
The 898 is good sized and nicely powered but I believe the 998 has a little more to offer than just size? If I could afford the extra I would get the bigger unit - Myself. I use mine to bass fish mainly KY lake so I am scoping out ledges and looking for balls of shad.