both have their use.
The portables are gasoline driven (with the attendant risks), use more fuel, and usually need to be run through an appropriate sized battery charger to get their full potential. Their DC output is very low. Since most battery chargers have a "power factor" (they need more watts of input than a simple calculation of amps times 12 volts), matching the charger and the generator must be done with some care and research. However, the gas portables are MUCH cheaper, and, if they need repair, are easy to get to the repair shop. The marine gensets you mention are diesel (safer, and if you have a diesel main engine, use the same fuel), use less fuel, and, in theory, should need less maintenance. In FACT, for whatever reason, lots of people find them troublesome....probably because they aren't used enough. Repair can be quite expensive, and, of course, initial purchase price is way more. I have had numerous friends who have loved or cursed at either kind! I, myself, have a small gas generator which I very rarely use. I have blessed it and cursed it, as well. Believe it or not, I have some very good friends who SAIL north from Cabo to California every year, and who have lots of gadgets using lots of power. They actually run their Yamaha gas generator underway, sailing, in the cockpit! Not my style, but quite inexpensive, so there you go. Anchorage neighbors are not likely to be in love with whatever generator you buy, incidentally.
