I would advocate
radar far and away over the
chartplotter in all cases. I'm not at all sure where this confidence in navigating by
chartplotter comes from. In my opinion, if you're navigating by
chartplotter in either restricted visibility or in conditions where you are unable to utilize more traditional paper
charts and navigation methods, you're most likely doing something wrong.
The idea that a
chartplotter is somehow of great aid in restricted visibility is pernicious and conveys a confidence that will prove ill founded. The Colregs dictate what proper procedure in restricted visibility should be and make no mention of
chartplotters.
Radar, on the other hand, is referenced and is a great adjunct to the human eye. And it performs the vital function of displaying targets unknown to any
chartplotter, ie..other vessels.
A stand alone
radar display makes sense in terms of reliability and lack of dependency on a combined unit. If you are an experienced operator of
radar you'll find little need for the chart overlay. If you find the overlay of essence, I'd wager your
radar skills and basic
radar navigation skills need some work. As mentioned above, one of the best ways to gain valuable
radar experience is in good weather. The
radar display should be familiar enough that it seems like second nature to operate it.