The biggest difference is that the Monitor does not have a remote, whereas the ST does. This is because the Monitor was designed for a mastering setup. The Monitor also has a built-in D/A converter, with 4 stereo inputs, whereas to have 4 stereo digital ins on the ST, you must purchase our DAC-ST. Monitor has 3 stereo Analog ins, whereas ST has 4 stereo analog ins (plus a stereo aux in). Monitor has 2 sets of speaker outputs, whereas ST has 3 speaker outputs, plus a stereo sub output. In the end, the decision comes down to features- sonically, the two devices are almost identical.