If you want just 2d, Down image and GPS then I would go with below. 5 inch for me is too small but 7 inch is large enough to see 2d maps and down. if you go Side image you would need at least 9 inch.
Humminbird is more user friendly in the menu's.
Humminbird Helix 7 Gen3. for $499.

Humminbird HELIX 7 CHIRP Mega DI G3