For me the choice MPPT controllers depends on specific use (Check the Midnite KID) or for a PWM only controller (Midnite BRAT), however it is correct in one part and that is the DC battery MPPT controller generally do only work properly provided the voltage from the PV is higher than the battery voltage, however there are controllers like the Midnite solar that can be configured as in what is effectively PWM only, they're one of the most flexible controllers around for a battery controller.
However it is incorrect saying that Grid MPPT inverter only boosts voltage, that is not the case it will, but it depends on the string voltage being used they will either buck or boost, in general though any MPPT unit works better if dropping from a higher voltage to a lower voltage with increased current.
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