I have a Hummingbird 597 with downscan. This is a primitive unit compared to what is on the market now. I like the down imaging it provides, but I would LOVE to have side imaging and would prefer it over DI, if I had a choice. I think that side imaging would provide a more useable image. There have been some side imaging pix posted on this forum that have been fantastic. I'd say, go with side imaging, or even better, both!