For me there's no comparison. My 2 cents...
- That video processing chip does make a difference in the quality of the upscaling. It does a better job at Upscaling to 4k and adding HDR to Blu-Rays and DVD's as well. Most reviews put the quality on the UB820 above the lower model. It's actually the same video chip as in the UB9000.
- The build quality is better and it has a front info display. A big difference alone for me. I hate players that just look like a cheap black plastic rectangle or square. SO cheap looking. And I believe the remote is better, although it's still a bit lackluster for the price point.
- It also has dual HDMI outputs which is BIG for certain A/V setups (can use one for video to TV and one for audio if you have an older AV Receiver that doesn't support 4k). That was a big one for me till I updated my AVR a year or so later where as now I don't need it.
- The streaming features are super outdated, but Wifi can be a big deal if you care about keeping the player's software updated with improvements over time. Without it, you won't know there are performance updates without going online, and then you'd have to download the update to a USB drive and install it manually. That alone too would be a deal breaker for me.
I would really say too it comes down to the rest of the quality of your A/V setup. If your TV isn't a top notch OLED (LG/Sony/Samsung) or Samy's top QLED maybe you won't see as much an upgrade with the video. And for audio, if your the movie enthusiast content with a "soundbar" and don't have a high end AVR and speaker setup then probably save the money.
The 820 was like $350 on Amazon I think during Black Friday. That was a steal!! I paid I think $420, which at the time several years ago was the lowest it had ever sold for.