My current boat has a MinnKota charger as that's what came with it from the dealer and sofar it's been good.
On another new boat I bought back in '99 I installed a Guest charger and that one has been flawless, even now after 13 years of service and another owner of the boat.
If I was to recommend a charger today, or if I was buying another one, it'd definetely be a Guest without question.
I've heard negatives about alot of different chargers on the market, but I've never heard a bad word about Guest.