Which is better for PS5 gaming?

The A90K. Sony rates its input lag as low as 8.5ms and it has four HDMI inputs, so a console, soundbar and streamer can stay connected. The BRAVIA 8 also does 120Hz and VRR, but its single listed HDMI port is a real limit.

Is the BRAVIA 8 worth stepping up to over the A90K?

Yes if screen size and a newer processor matter most. The BRAVIA 8 gives you 55 inches, 2024 processing and Voice Zoom 3. The A90K wins on ports and gaming lag.

Which has better sound?

They are close. Both use Acoustic Surface Audio+ with actuators behind the panel. The A90K adds a center subwoofer and Acoustic Center Sync with Sony soundbars; the BRAVIA 8 adds Voice Zoom 3 for dialogue.

Neither has a published lifespan edge. OLED panels age with use, and the BRAVIA 8 is two years newer, so it starts with more headroom. Owner ratings are similar: 4.7 for the BRAVIA 8 and 4.6 for the A90K.

Which fits a small room better?

The A90K. At 47.5 inches and 13.4 kg without the stand, it suits a bedroom, study or desk. The 55-inch BRAVIA 8 needs more wall or stand space.

Do both support Dolby Vision and Dolby Atmos?

Yes. Both handle Dolby Vision, HDR10 and HLG, and both decode Dolby Atmos. The BRAVIA 8 adds DTS:X support.

Sony BRAVIA 8 55-inch OLED TV vs Sony BRAVIA XR A90K OLED TV

Both are Sony OLEDs with 120Hz panels, Dolby Vision and Acoustic Surface Audio+, so picture character is close. The BRAVIA 8 is the newer 2024 set at 55 inches, with brighter XR OLED panel, Voice Zoom 3 dialogue clarity and the Sony Pictures Core film library. The A90K is a 2022 48-inch model with four HDMI inputs and a documented low input lag for PS5 play. Buy the BRAVIA 8 for a larger, brighter main-room screen; buy the A90K for a smaller room or a dedicated console setup where port count and lag matter.

Choose the BRAVIA 8 if you want the bigger 55-inch picture, the newer 2024 processing and clearer dialogue for a living room.
Choose the BRAVIA XR48A90KB if you need a compact 48-inch OLED with four HDMI inputs and very low input lag for gaming.

Prices

Sony BRAVIA 8 55-inch OLED TV: $1,398.00 at Amazon (checked today)