I have an older Garmin 76 CS which is a waterproof, floating, handheld GPS which I had bought use for less than 1/2 the new price. It's features are pretty much the same as the 60 series. I have also used the 60 series which has a far more ergonomic design. The 60 series is also waterproof, but doesn't float, so if you go with it be sure to tether it when boating . If I were to choose between the 2 if at the same price, I would go with the 60 series, because the ergonomic advantage is that significant.
The handheld units work well for their intended primary purpose which is non-motorized travel. With the faster speeds of motorized travel, there definitely is a huge advantage to the larger screens of the fixed units which allow you to see a bigger area of the map while at a given magnification.