Any structure vision is ideal. I have used the majority of all products and brands and prefer to run with DI and SI majority of the time. if you only want one screen up at a time then SI can work well once you understand how it works, then on 455 khz is ideal for closer in stuff too so you still kind of get a decent view of the bottom below you. Down Imaging is what I mainly focus on for most lakes looking for fish and variations of depth changes and stuff definitely on a small screen. Once you perfect the use of Side Imaging though there is nothing compared.
I though prefer to have both showing SI and DI at my console. In front of the boat I run Down Imaging next to Chirp sonar, which in my opinion isn't all what it's cracked up to be. I just have it on due to having enough space on a lowrance touch 12. If I had to pick one though I'd pick the structure scan because it is going to be showing you a lot more of what you really care about.