The higher clockrate (8MHz vs the A500/A2000's 7.14MHz) 68000 did little to improve software performance.
Indeed, the sound chip IMO was terrible compared to the mighty Paula and that tiny bit of extra CPU time was not gonna make the difference when you started using sampled sounds, that took CPU time. The C64 even had things the ST didnt, eg: hardware scrolling .
I had an STE for a very short time, never liked it, glad i got rid of it.
-edit errr oh umm be quiet Calen :-)