Very similar. The C64 hardware was better, with a dedicated audio chip, better color and (IIRC) hardware blit support for sprites. Much better keyboard, too.

But it was double the price, putting it out of reach for many more families than the Spectrum. This made a kind of critical mass that lead to a huge community around the spectrum in the UK. And a fantastic burst of creativity as the barrier to entry to writing video games dropped as low as it would ever get.