The Pronautic is a good charger, I've installed countless units and while less than a handful failed prematurely, the failure rate is very small and no worse than any other brand that I've installed. They have some great features too. Their biggest enemy, like all electronics, is line voltage. While they deal well with low voltage supply and actually have options to customize output based on such, they're susceptible to poor utility regulation, marina conditions, and natural phenomenon such as lightening. But that's all smart chargers and any on-board equipment that has a circuit board. While ferroresonant chargers had their downsides, they were very robust and certainly better at handling this particular issue. BTW, don't right off ferroresonant chargers, they've made some advances in recent years that are slowly making them more attractive but aren't quite there yet IMO and may never be simply due to physics but they're not the same as they were years ago. Having said that, they now incorporate circuitry to overcome some of the old downfalls which I suspect makes them just as susceptible to the same conditions affecting fully electronic smart units.
I would also recommend going with the 60A unit if you're upgrading. As Bud said, the math isn't as simple as it seems to replenish in a timely manner what's been drained. Consider it carefully as now's the time to upgrade. If you do decide to upgrade output (or not), measure the length of each circuit and see if the wire will handle full charger output. That's taking the length of each bank's charge wire and the single return ground back to the charge. This must be done for each bank. Use the size of wire for all banks that was calculated for the longest run. Don't worry about the AC supply wire, it should be sufficient for the 50 and 60A units but just to be sure in case someone screwed up, ensure that it is at least 14/3 wire. Read the instructions carefully and you MUST install the chassis ground wire. Your current unit may or may not already have one but it too must be a specific size for the application. Each bank's output needs to be fused, this may already be part of your vessel's charge circuitry. And you'll have a temp probe to install.
There is such a thing as too much charger for the bank in a given application. Outputs that are too high for the bank size will fry batteries. Your typical charger isn't much of a concern as they're typically between 20 and 60 amps on average but inverter/charger units can get into the 100's of amps output. This is fine for very large inverter banks but I've seen high output inverter/chargers with small banks, not good.
I would also recommend installing the Pronautic remote display. I installed it in my boat and am glad I did. It allows you to check the current charge cycle status, output voltage, current, etc. without opening up the engine hatch. It's not a battery monitor so it won't work without AC power but you already have that anyway. I know you like monitoring stuff