The use of Mode1 enabled the CPC to keeps the same graphics as Spectrum, in appearance only. While the square pixels looks almost the same, the code was completely different. Also, the CPC being set for a 320x200 display instead of a 256x192 display, the pixels are in fact smaller on screen, hence a bigger border was needed for the exact same resolution.
This (the larger border) led to the false argument that this was the CPC resolution and therefore it was inferior to the Spectrum one, although the amount of pixels on the screen is EXACTLY the same.
While some Spanish companies reduced the screen in order to get the game better running in low-spec 464, the infamous speccy ports just ran a reduced screen so the ZX Spectrum's code and graphics could run almost "unchanged".