Which is better for a bright living room?

The Samsung S90HD. Its Glare Free coating suppresses reflections that show up on the LG C6's glossy panel.

Which is better for gaming?

The Samsung. It reaches 165Hz and supports both G-SYNC and FreeSync Premium Pro; the LG C6 is a 120Hz set.

Does the LG C6 come in smaller sizes?

Yes. It is offered in 42, 48, 55 and 65 inches, while the Samsung S90HD is a 65-inch model only.

Which has better sound?

The Samsung, which uses Object Tracking Sound Lite with Dolby Atmos. The LG relies on standard built-in speakers, so a soundbar helps either set.

Is the step up to the Samsung worth it?

If you have a bright room or a gaming PC or console, yes. If you need a smaller size or Bluetooth audio, the LG C6 fits better.

Both are OLED panels with similar lifespans. The LG C6 includes a six-year protection plan versus five years for the Samsung.

LG C6 OLED 4K Smart TV vs Samsung S90HD OLED 4K Smart TV

Both are 120Hz OLED 4K TVs with four HDMI ports, so picture fundamentals are close. The Samsung S90HD adds a glare-free coating, a 165Hz gaming mode with G-SYNC and FreeSync Premium Pro, and Dolby Atmos object tracking sound; the LG C6 counters with Bluetooth, an AUX input, and a wider choice of screen sizes from 42 to 65 inches. Buy the Samsung for a bright room or serious gaming, and the LG if you want a smaller set or need Bluetooth audio out.

Choose the LG C6 if you want a 42, 48 or 55 inch OLED, need Bluetooth or an AUX connection, or want the longer six-year protection plan.
Choose the Samsung S90HD if you watch in a bright room, play games at high frame rates with a PC or console, or want Dolby Atmos sound.

Prices

Samsung S90HD OLED 4K Smart TV: $1,047.99 at eBay (last seen Nov 9)