Which is better for PS5 or Xbox gaming?

The C5. Its 144Hz refresh rate, VRR support and four HDMI ports handle consoles better than the B6's 120Hz panel.

Does the B6 support Dolby Vision?

The listing only says HDR. The C5 explicitly supports Dolby Vision, HDR10+ and HLG, so it is the safer pick for Dolby Vision streaming.

Which has more screen size options?

The B6. It comes in 48, 65, 77 and 83 inches, while the C5 here is 55 inches only.

Is the C5 worth stepping up to from the B6?

Yes for gamers and Dolby Vision viewers. The C5 adds 144Hz, more HDMI ports and anti-glare, which the B6 does not list.

Which is better in a bright room?

The C5 lists an anti-glare coating and a wide viewing angle. The B6 does not specify anti-glare, so the C5 is the safer choice for bright rooms.

Do both have voice assistants?

The B6 lists Google Assistant and Siri. The C5 listing does not specify assistant support, so check that if voice control matters.

LG OLED C5 Series 4K TV vs LG B6 OLED 4K Smart TV

The LG C5 is the stronger TV for most people. It has a 144Hz panel, four HDMI ports, Dolby Vision and HDR10+ support, and a wide viewing angle that holds color off-axis. The B6 is a step down in brightness and motion handling, and its 120Hz refresh rate and smaller port count matter for gamers. Owners and reviewers consistently rate the C5 series higher for picture quality and gaming features, while the B6 is a solid OLED for casual viewing in a bright room.

Choose the LG C5 if you game on a console or PC and want 144Hz, VRR and four HDMI inputs, or if you watch a lot of Dolby Vision content.
Choose the LG B6 if you want a smaller 48-inch OLED or a larger 77/83-inch screen and mostly stream shows and movies at 120Hz or less.

Prices

LG OLED C5 Series 4K TV: $895.99 at eBay (last seen Nov 9)