I definitely like ACR/VSRs (you can't beat the convenience) but am a larger advocate of an AC shore charger and an ACR/VSR will in most situations create more dependency on a charger. I don't like the approach taken by some of the ACR/VSR manufacturers. In order to provide total dual bank isolation (independent profiles and programs on two banks with decidedly different impedances due to different usage) a supplemental switch is often required. So if you're on a budget and have a limited tolerance for technology a simple dual battery switch is fine. In fact with a fundamental understanding of charging systems a single switch can be used to manage alternator protection, extend battery(s) lifespan and provide AC charging isolation. There's no such thing as a perfect charging system and every design has inherent conflicts but we try to minimize them.
Here's just one small example of system efficiency and the resulting cause and effect. Say we take a woofer with a 2000 watt thermal rating. Its beefed up to take alot of abuse. The surround, cone, spider, voice coil are all much heavier as a result so it takes 1000 watts to reach its potential. That's alot of mass and inertia that has to change directions 200 times a second not to mention the finer nuances multiplexed within the big signal. So its kind of clumsy and inarticulate from a musical standpoint although with enough power it can seriously move air and ultimately play very loud. And this comes with a major premium in current draw. As a result the 14 plus volts at the alternator are only 12.5 volts at the amplifier primary inputs when the sub is driven hard. As voltage drops so does the real power of an unregulated amplifier and thus the entire system is affected including the highpass amplifiers. Not everyone can afford four stereo batteries and an upgrade 150 amp alternator to stiffen the voltage and overcome an inefficient design.
There are numerous areas where you can profoundly impact system efficiency. A more efficient system is immediately recognized by a more open and dynamic sound and may actually sound better than a much larger or expensive system. When you're operating within a budget you can ill-afford system design and implimentation errors compared to someone who is throwing away more resources that tend to mask some of those flaws. The best sounding systems make far less waste and eliminate the performance bottlenecks that choke the other components. Balance and selection is part of it. System tuning is huge. Hope this helps.