I always say bigger is better! I have a helix 7 Mega and it’s awesome, but if you could get a bigger screen, do it. Side Imaging cuts down on the search time dramatically because you can see what’s out to the side of you instead of what’s below you. The best coverage you can get with 2d sonar is seeing as much bottom as your depth. 20ft. of water means 20ft cone of bottom you see. But 100ft of side imaging shows you 200ft of EVERYTHING in the water, not just the bottom.