[MarkSF]

My suggestion would be to find a large West Marine store, and have a look at a few models. Try a few basic functions like navigating to a waypoint. This will give you a feel for ease of use.

My Lowrance HDS 5m has a great feature set, but I find it a bit tricky to use. Hardly the most intuitive interface.

 

[MarkSF]

One feature I really love on my Lowrance is the projected course. I have it set to project a line one mile ahead. This can be very handy in SF bay, showing you how the current is really affecting you.