SMPS Vs. Regulated Power Suppy

A switch mode power supply (SMPS) is a regulated supply. I assume that by "regulated", you mean linear dissipative regulation. An SMPS regulates by producing varying magnitude or duration pulses and then averaging those pulses with a passive filter to produce the regulates output or outputs. Since the pulses are at fairly frequency, isolation through a transformer can be done at this stage with transformers that are a lot smaller than 60 Hz ones.

This process can be quite a bit more efficient than simply burning up the excess voltage in a linear regulator, but it also is a noisy process. However, this is not all bad. By the time the filters convert the power pulses to DC, they are also capable of filtering out lots of line side noise. So while the regulation process in a SMPS is not as inherently fast at correcting output errors, the filters can often beat the high frequency attenuation of linear regulation control loops.

By the way, here is a tutorial on linear regulation: