That makes comparisons a bit easier. Each OLED uses the same panel made by an LG factory, so the picture quality difference between one OLED and another OLED is very small.
This is a stark difference from LCD TVs, that often use completely different panels produced in different factories.
So what separates X OLED to Y OLED? Picture processing, aesthetic design, smart TV and connectivity.
LG OLEDs are the most all-round future proof TVs, they have the most up to date connectivity and great smart TV. Picture accuracy out of the box is good. They have good upscaling, but their motion is their biggest weakness. Some people get along with it more than others. With LG the BX has worse upscaling than the CX and up, whilst the GX is the first to come with improved sound. The WX is the premium TV with a dedicated soundbar.
Panasonic OLEDs differ from LG with picture processing and picture accuracy, their motion has less complaints and their TVs are the closest to the director's intent out of all OLEDs. They do however have a more basic smart platform and older HDMI connectivity. As with LG they have base models like the HZ980 and HZ1000 but you need the HZ1500 or higher to get better sound. The HZ2000 is a special TV with tweaks to brightness and power to make it have brighter HDR picture quality.
Philips strength is with motion. Upscaling is very good also. They have good picture accuracy. They run Android TV which isn't fantastic, but they have ambilight which some people enjoy. With their models the 8 series is the base in 2020 whilst the 9 series has better audio built in. Older HDMI connectivity on these models.
Sony's strength is with motion and sound. Upscaling is very good also. They have good picture accuracy. They also run Android TV but unlike Philips all of their TVs come with good sound built in with their acoustic surface technology. Older HDMI connectivity on these models.
Overall you'd have to study the TVs side by side to notice a difference, so its really just a matter of which ticks the most boxes for you, there's no one-clear-winner.