Draw/refresh speed of different ST7789 displays

[Robecq]

hi,
I am using a ST7789 display attached esp32 s3 wroom cam, which is streaming images. works well achieving up to 27 FPS. I have 2 different displays using this driver to choose from, both at 240 x (2.4' GMT024-08-SPI8P v1.3 and 2.0' TFTSPI GMT020-02 v1.1), both work but one is unable to maintain the frame rate of the other. My question is what is determining the slower/faster FPS on the different displays when the board and code is identical?