I would think if you fish much shallow water to definitely go with SI. If you mostly fish deep water then the DI I think would be the one to go with. I have done a lot of research lately and I went with Humminbird 899ci HD SI. It is selling for almost half what it cost last year and you can get a 2 year warranty now with the Humminbird select program going on right now. That's my 2 cents worth hope it helps you on your decision.