Some people feel more comfortable buying something they know isn't top notch because they feel it can take care of their needs without them having to learn how these individual devices work
I actually feel like I bought a top-notch unit in many ways with the MPP unit I bought.
I didn’t and don’t expect early failure. I
recognize that it isn’t top-shelf in price nor is it top shelf in branding penetration, and the price also suggests the engineering R&D doesn’t require a lot of money in payback. All of those misding characteristics are present in top-tier brands.
Nevertheless I selected the AIO for several reasons, and yes price was a notable consideration. But it offered the SCC parameters I required, has a small footprint, I didn’t need to plan any cabling, and it integrated perfectly for SBU usefulness including a built-in substantial battery charger. The biggest downside is I had a 12V requirement and have/had cabling to support 2500W but the unit has a meager 1kW inverter. I do have a separate 2kW psw inverter so that was not a deal breaker.
With all the other advantages and its very positive user reviews I selected it anyway. FWIW: If it cost the same as or more than mid-shelf, mid-priced components the auto transfer and built-in charger would be the only advantages and probably I wouldn’t have spent for an AIO.
AIOs are also scalable and can meet redundancy thinking as well as mentioned.
AIOs have a place in consideration of a buildout.
Having said that, my about-to-be-installed upgrade to 3690W of panels will sideline the AIO- I’m using two SCCs, the separate 2kW psw inverter, and may not ever need grid backup connectivity again for this circumstance. When I build the house a larger (or two) split phase AIO will be in the running again for the same reasons listed above. Not only that- by the time I bought components, transfer switches, and sub-panels, I can have money leftover with AIOs and enjoy 0-second ups-like switchover for grid-down situations; grid may be unnecessary 9+ months of the year for household use (though convenient for welders, tablesaw, other big stationary tools)
That’s why AIOs are viewed positively by some: advantages hard to dismiss in a build that have nothing to do with electrical competency.
*EDIT
Realistically, I could have added a second 1012LV-MK for the same output as the separate 2000W inverter. Monetarily, a second AIO would make sense, too, as it would only be $100 more than the combined cost of the 6420AN and 4215AN I purchased but at the time I ordered stuff there were no 1012LV’s in stock. I could use the SCCs in both units simultaneously, only turning on the second AIO when more than 1000W is required (at ~27W idle consumption for the 1012LV’s, each, that’s not terrible but is a factor to consider this time of year. The 2000W psw inverter is 11W idle consumption… or 20% of the AIOs, combined. The 2kW inverter’s fans are quieter and run less often, though the 1012LV’s fans are variable speed so not often that obtrusive.)
Do you see why the AIO’s are attractive, now, even for small systems?