You can find C9 vs. A8G discussion in several threads.
Here's my summary from the A8G thread, reposted here with edits:
If you're a fast-twitch console gamer, buy the LG for HDMI 2.1 support and lower latency.
If you want to use the TV as the "hub" of your system (rather than an AVR or pre/pro), buy the LG because the A8G only has two full spec HDMI ports that support [email protected]
If you predominantly watch SD and HD content, buy the Sony.
If you want to use the TV as your center channel speaker, buy the Sony for its screen-is-the-radiating-surface speaker. Even though the audio quality isn't up there with a good dedicated center speaker, it's pretty neat having dialogue sound like it's literally coming from the mouth on screen.
Otherwise, I think it's a bit of a toss-up. They use the same panel, so they have very similar picture quality. There are minor differences when comparing like presets, but I think these would disappear when calibrated. Some people have strong opinions about webOS vs. Android. I have a Roku Ultra and Nvidia ShieldTV, so I didn't care much about the TV's apps. Also, some like the Sony's stand better, and it's a little cheaper at the moment.