I have three batteries in my boat (two for the TM one for lights and instruments), and initially had a one bank charger which was a pain to keep batteries charged, then I went to a went to a 2 bank battery tender and kept the third battery in the house and charged it there.
I finally got tired of screwing around with connecting and disconnecting batteries and bought a Pro Sport 20A 3 bank charger which I sent back. It was too large to fit well in my boat, it ran VERY hot, the output cables were EXTREMELY stiff and hard to manage, and it had no visual indication of the state of charge. Flush...
I wound up with the Noco 3 bank (12A) which I've secured to the transom wood. It's smaller than every charger I looked at, waterproof, and charges all my batteries overnight if I go fishing the next day.
The reason I did not buy the 30A Noco is I'm using small 35Ah batteries and have no need for 10A per bank. If I did use large batteries and needed to charge them overnight I would have considered the 30A model but as it is for twice the price on the 12A model it wasn't a serious option.
PS, I too read of the MK charger issues and decided against them as the Noco chargers got generally stellar reviews, I'm happy I did.