Sure was a wild and woolly period of computing - so many wonderful machines, too many different ways to develop things. Just like today, only cuter ..
Then the whole lot got eaten by the PC.
Just mention that comparing MHz is not quite right in that era. For example Speccy's 3.5MHz were not that much of an advantage compared with the 1MHz of the C64 if you take into account that it didn't have hardware sprites and all had to be implemented by software, 48K models didn't have dedicated audio chip, etc.
Sound wise the C64 was better but in terms of speed the Spectrum dominated.
Of course, it goes without saying that the spectrum was best.
I had a ZX Spectrum +2A back in the day and I've programmed several games for the speccy, and the attribute clash was a pain :)
It was a great time to be interested in computers. Much complexity, many options, and so little time .. which eventually ran out for all of it. Only a handful of us are still using these machines for things these days..