I have used both when I was a kid. There were nothing alike really.

I owned a BBC Micro Model B (was given one when a friend was given a 486 PC) and I used the Archimedes at school. The BBC Micro was archaic compared to the Archimedes and PCs of the time.

Of course it was.

It was six years older and this was the era when CPUs evolved massively from one generation to the next. Just like the Acorn 'Atom' was 'nothing like the BBC Micro' in spite of using the same processor.

For some contrast: when the BBC Model A came out in 1981 originally it had cassette tape as mass storage, an 8 bit cpu clocked at 2 MHz, 16K RAM and if you were very lucky yours came with the optional floppy drive which cost nearly as much as the machine itself. When the first ARM was sold to the public, six years later it came with a 32 bit RISC CPU clocked at 4 MHz, 512K or 1M of RAM, an ST 506 based harddrive option.

That's just six years of progress, and we're skipping over many steps in the lineage, the BBC Master series, the tube expansions and the Olivetti saga. You could pick 1980 to 1990 and write a pretty large book about personal computing progress during those years and you likely would still miss important events.

But the lineage was - for those that owned all of the intermediary machines as well - pretty clear, and that is before we get into the lineage of the software that the Archimedes shipped with, MOS and BBC Basic, which both worked more or less as you would expect given the new machines capabilities.