Which is better for gaming?

The LG C4. It has a 120 Hz panel with VRR and Nvidia G-Sync certification and four HDMI ports. The Sony listing does not state a refresh rate or gaming features.

Which has better sound out of the box?

The Sony bundle. It includes the Theater Bar 7 soundbar and Sub 7 subwoofer. The LG relies on built-in TV speakers.

Is the bigger screen worth stepping up to?

If wall space allows, the LG's 83-inch panel is noticeably larger than 77 inches and adds gaming features. The Sony offsets that with included audio.

Which smart TV platform is easier to use?

Both are well regarded. Sony uses Google TV, which leans on Google search and casting. LG uses webOS with its own launcher and magic remote.

Does either handle glare well?

The LG C4 is listed without an anti-glare coating, so bright rooms may show reflections. The Sony listing does not specify its coating.

Sony BRAVIA 6 77" OLED TV Bundle vs LG C4 83" OLED TV

The LG C4 is the better TV on its own: a larger 83-inch Evo OLED panel, 120 Hz refresh with VRR and G-Sync certification, and four HDMI ports. The Sony bundle wins on total system value because it pairs a 77-inch OLED with a soundbar and subwoofer, so you skip buying audio separately. Buy the Sony if you want one box with strong sound; buy the LG if picture size and gaming features matter most.

Choose the Sony BRAVIA 6 bundle if you want a complete 77-inch OLED setup with a soundbar and subwoofer included and you mostly watch movies and shows.
Choose the LG C4 if you want the biggest OLED picture here and need 120 Hz gaming features like VRR and G-Sync.

Prices

Sony BRAVIA 6 77" OLED TV Bundle: $2,899.98 at NFM (last seen Nov 1)