I havn't owned those exact two models but currently own a Piranha 175, 176 a 581 and a 767. ( Yea, I like my humminbirds!) The two you mentioned are part of the same series as the 176 and 581.
My 2 cents:
500 series: bigger sharper screen, (Great!) quick detach and fully adjustable mount ( with internal electrical connections), reliable as a hammer. Very good detail. Never found color to be a "gotta have".
Piranha series: Compact, low battery draw (100ma in black/white. 220ma in color), simple operation, reliable. Basic mount is more cumbersome to connect/unconnect and more difficult to adjust.
My advice: Go with the 500 series if you are mounting this in anything bigger than a kayak where space is scarce. That said, if you like the compactness of the Piranha series, consider the 176i. It's not color but adds GPS which is VERY handy, uses less than 1/2 the power and has a slightly bigger screen than the 195c as well. Price is a wash.
hth.
My 2 cents:
500 series: bigger sharper screen, (Great!) quick detach and fully adjustable mount ( with internal electrical connections), reliable as a hammer. Very good detail. Never found color to be a "gotta have".
Piranha series: Compact, low battery draw (100ma in black/white. 220ma in color), simple operation, reliable. Basic mount is more cumbersome to connect/unconnect and more difficult to adjust.
My advice: Go with the 500 series if you are mounting this in anything bigger than a kayak where space is scarce. That said, if you like the compactness of the Piranha series, consider the 176i. It's not color but adds GPS which is VERY handy, uses less than 1/2 the power and has a slightly bigger screen than the 195c as well. Price is a wash.
hth.