We investigate the dynamical properties of photo-thermal Self Electrooptic Effect Devices (SEEDs) fabricated of thin single crystal platelets in a wide region of excitation intensities at room temperature. Detailed characteristics of the switching processes and dynamics are precented for optical and for the first time for electro-optical types of bistable operation using an improved contact geometry. The role of the substrate of the SEED is also taken into account. It is shown that in the case of rectangular excitation pulses of light or of voltage the switching process can be divided into two regions, namely the crystal reaction time and the switching time itself. Both depend sensitively on the applied optical or electrical pulse height and also on the initial preheating. Critical slowing down is observed in the optical and the electrical case.