The Speccy was great, but yes the Amstrad graphics were better. Not because they were anything spectacular, but because the Spectrum suffered from colour clash.

In summary, the foreground and background colour (known as the attributes) could only be set at a resolution of an 8x8 block of pixels - so every pixel in each 8x8 block had to share the same colours.

This meant for example that as a yellow sprite entered the same 8x8 block as a green thing, then when the code set the colour attributes to yellow (for the sprite) the green thing turned yellow too.

The opening seconds of this video [1] show it pretty clearly.

[1] https://www.youtube.com/watch?v=1PI6GwKVAeY

Disclaimer (which I feel appropriate given the old school playground wars about which was the best platform): I had a CPC464 which I loved and still run emulated, but also often went round to mate's houses for Speccy gaming too.