So I understand these isolators have solved the energy robbing issue that older style diode isolators have. Supposedly they only take 1 to 2% of your alternator output whereas the diode type can take away as much as 70%.

I'd like to get one so my house battery gets topped as I run and so both of them stay full while my boat sits between uses. I'd be spending quite a lot more to get a good onboard 2 bank charger with a fair amount of amps. I'd want a 20 amp which is 10 x 2 . And I'd love it if that had distributing technology which sends the power where it's needed. Not just 10 amp maximum.

My boat has a group 27 for starting and a 24 for house. They are marine batteries. Not true deep cycle, but they do have marine crank ratings. I'd call them hybrid. The 27 is an Interstate and the other is a parts store brand.

I can go on with separately clamping my Schumacher 15 amp smart charger to the batteries, one after the other, but I'd like to just hook it up once and leave them both on maintenance charge once they are topped.

Supposedly the Victron isolator allow each battery to top up to it's desired level without issue.

Any arguments for or against?

Diode isolators work fine. Not sure where they got a bad rap. But, sure, a switching solid state solenoid isolator can perform better (while containing moving parts and contacts that do incur wear over time).

Many brands of multiple battery chargers, but you should stay far away from older "dumb" chargers. Newmar smart chargers are the top of the mountain, but are pricey.

Pro mariner flyback chargers are great, and there are some manufacturers who sell to the bassboat market that make some nice stuff for reasonable prices.

I decided to be a cheapskate, ordered a second Schumacher smart charger. So both batteries can stay on charger while boat sits between uses. I'm a day dunker who gets maybe 6 or 10 overnights per year.

That Victron is still pretty intriguing to me.