These options affect how PowerSUITE^®  controls the power-amplifier feedback bandwidth during an experiment.   Bandwidth is a measure of how quickly the control amplifier can “keep up” with a rapidly changing applied potential without degrading the signal.   In Maximize Speed mode, the potentiostat has a higher bandwidth than Maximize Stability mode.  This allows the potentiostat to be faster in applying a given potential, however it can cause oscillations with some cells.  Maximize Stability mode is less likely to cause oscillations so it is most often the preferred choice.  It is also the default setting (checkbox unmarked) for the Override Auto E Feedback. 

The Differential Feedback setting (PARSTAT^® instruments only) sets the electrometer control circuitry to a true differential setting, where the potential is controlled between the Sense and Reference leads.   This setting is preferred when performing either a) true four-terminal experiments (such as controlling the potential across an interface between two reference electrodes), or b) higher current experiments (>100mA).  For the latter, the differential feedback configuration eliminates the voltage (I x R) errors associated with the high currents (I) combining with the resistance (R) of the working electrode lead. 

For the 263A and 283 systems, setting the E Feedback to Maximize Speed sets the system to differential mode as well, which is why the Maximize Speed is required for the 2A option (high currents) in 263A systems (A four-terminal cable, part # C0366, is available for the 263A that makes the sense connection available ) for correct voltage measurement/control.   The 273A always uses differential feedback, but requires that an additional lead be used at the Sense connector of the electrometer (in place of the shorting plug) when measuring/controlling high currents.