I personally won't use an onboard charger. The studies I have seen have shown even the best ones aren't as good or durable as the cheap typical portable chargers. And I don't have to worry on multiple day tourneys when one goes out.

I have been using the CSI onboard Charger in my boat since January 2006 and it is plugged in all the time and have had Zero Problems. If something ever does go wrong with it I will install another just like it.