The all-in-one units offer a couple of advantages to those new to RV upgrades.
1. Less wiring - This cannot be understated as wiring is the most tedious and time consuming part of the install, at least for me.
2. Simplicity - Less research of individual components, less shopping around, less to manage
Disadvantages
1. Costly to upgrade - Say you want to double your solar panels. The entire all-in-one may need to be replaced instead of just an MPPT device.
2. One size does not fit all
I don't own an all-in-one and never really considered one. The above are my observations of experiences posted by other forum members.