Which is better for gaming?

The Samsung S95H. It runs up to 165Hz, has four HDMI 2.1 ports and the lowest input lag tested. The LG B6 is fine at 120Hz with FreeSync and G-Sync, but it is the slower set.

Which has the better picture?

The Samsung. Its panel is brighter and holds color better in a lit room. The LG B6 wins on Dolby Vision, so Dolby Vision movies look better on it than on the Samsung, which lacks that format.

Is the LG B6 worth stepping up to for the bigger screen?

Only if screen size matters most. The 83-inch LG is bigger than the largest common S95H size, but you give up brightness, refresh rate and ports. The S95H also comes in 83 inches.

Both are OLED, so both can develop burn-in with static logos over years. LG's OLED Care features are aimed at protecting the panel. Samsung's brighter panel runs hotter, which can matter for long static content.

Do either support Dolby Vision?

Only the LG B6. The Samsung S95H uses HDR10+ and its own HDR Pro processing instead.

Which is better in a bright room?

The Samsung S95H. Its Glare Free coating and higher brightness keep the picture clear in daylight. The LG B6 is better suited to a dark room.

Samsung S95H OLED TV vs LG B6 OLED 83-inch 4K Smart TV

The Samsung S95H is the stronger TV for most people. It has the brighter panel, a 165Hz refresh rate, four HDMI 2.1 ports and much lower input lag, and its 4.8 rating from 1,000 owners backs that up. The LG B6 is the entry-level OLED line, so it gives you a bigger 83-inch screen and Dolby Vision but a dimmer picture, 120Hz and a thinner port set. Buy the LG only if you want the largest screen and watch mostly dark-room movies.

Choose the Samsung S95H if you game, watch in a bright room, or want the best picture quality for the money.
Choose the LG B6 if you want the biggest OLED screen and mostly watch movies in a dark room.

Prices

Samsung S95H OLED TV: $1,987.99 at Macy's (last seen Nov 7)
LG B6 OLED 83-inch 4K Smart TV: $2,999.99 at eBay (last seen Nov 9)
Difference: the Samsung S95H OLED TV is $1,012.00 cheaper than the LG B6 OLED 83-inch 4K Smart TV at the latest prices (Nov 7 and Nov 9)