Ease of Use: Connect up and get an 'ok' prompt, no complex tool chain or programs to install.
Speed of development: No write, compile, upload, run, test - just program.
All marketing for microcontrollers are concerned with processor speed - but what about development speed? What about ease of use? Surely if the processor is fast enough are not these two things important?
If like me you have been brainwashed into thinking that the fastest processor is the best even though only a few percent of its speed is actually used, then its time to wake up. My time is important, My ease of use is important.