There have been various models of the "original" ST - The ST (The very early model, with no TV modulator, and an external floppy drive) followed by the ST-F (internal floppy drive) and ST-FM (internal floppy drive and a TV modulator)
As TjLaZer said, the ST-E was meant to be the answer to the Amiga - like the Amiga, the ST-E had stereo sound, a palette of 4096 colours, hardware scrolling, and a blitter.
Unfortunately, some of the original ST limitations still remain - the fact that the ST's low resolution still only allowed 16 colours meant that getting the most out of that extended pallete range (by showing more than 16 colours on screen) still required coding routines to change the colour palette part way down the screen.
In addition, the ST-E's stereo sound allows playback at fixed sampling frequencies only (6.25 KHz, 12.5 KHz, 25 KHz and 50 KHz). While this means that the ST-E can generally play back better quality samples than the equivalent Amiga, playing a sample back at different frequencies than it was recorded at needs the CPU to stretch or shrink the sample data - e.g. if you sample a piano playing an "A" (440 Hz) at a 6.25 KHz sampling rate, and you then want to play it back as a "C" (approx 523 Hz), the ST-E needs to chop out slices of that sample, as it's still playing it back at 6.25KHz. AFAIK, the Amiga simply increases the playback frequency of that channel to 7.4 KHz-ish (this may be wrong - I might be misunderstanding exactly what the Amiga can do with its sound output)
Also, the ST-E's stereo output is purely a 2 channel system, so playing more than 2 samples together (for example, playing a MOD file) requires the CPU to mix the sample information together.