Average current mode control vs peak current mode control
It's harder to implement cycle-by-cycle current limiting in average current mode.
Also:
With average current mode control you have the problem of sensing the current.  You have to have a sense resistor or network across your inductor and extra circuitry, leading to higher cost and complexity.
With peak current control a simple sense resistor at the bottom of the switch (for buck) can feed directly into the current sense amplifier, so it's easier and cheaper.  You do have to implement slope compensation, but that's easily done.  Noise issues due to low duty cycle can be mitigated with valley mode control.