Ok, I figured it out. The only difference between the Chirp and Plus model is that the Plus is touch screen. Nice to jave, but not worth an extra $300+ just for touch.
And thanks ohboyitsrobby. After a little more research, I just bought two of these even though sideview isn't needed on my trolling motor. I will just use 2D sonar and down imaging. Can't beat a 9" screen for that price.