- How it is to Watch 4k compared to 1080p?
Yes noticeably better as long as you are close enough to see it or your 4k tv is big enough
-How well it handles 720p and 1080p?
No problem there at all, does 720p better than 1080p sets. Totally fluid motion as the set has a quad core logic board with a 1000 interpolation rate and the LG panel has a very low pixel response rate as its IPS.
- How it handles SD content?
Depends on the quality of the SD content. Something like a superbit dvd looks really good but a very low bit rate terrestrial channel can look weak but this depends on the tv I guess. Some do a better job of upscaling and cleaning SD material even low bitrate material.
- Input Lag is a problem for gaming?
Mine is 31ms in game mode. I think the lowest is about 19ms which I've seen on a Samsung. Worst one's can be 50-70 I think and a few rare examples worse than this especially tv's without a game mode.
- Where do you get your 4K content from?
My tv has a 4k youtube app built in plus I have an android box with 4k output. The tv also plays 4k content via usb or dlna and I download 4k videos and store them on a nas drive. Lastly a pc that outputs 4k but can only do so for older games and media.
This is my tv only a budget set but performs better than many mid-range sets at the time I bought it. About a year ago. It uses a LG panel as the tv features passive 3D
https://finlux.co.uk/media/wysiwyg/Product-manuals/49UT3E310B-T.pdf
http://www.displayspecifications.com/en/model/deb17bd
LG seemed to have stopped supplying 3D panels to third party companies now so I'm totally happy to have got it when I did. It cost me £390 including a quad core android tablet which I only got because the first delivery got smashed as the delivery man dropped the tv from the back of the truck. So effectively 330 really. Tablet was easily worth £60. You can also use the tablet to control the tv or stream from the tv to the tablet in any room of the house (has to be on the same network connection) or use the tablet as wireless headphones if you desire etc. All the normal wireless stuff like streaming the tablet's own display to the tv using wifi direct. It includes 4 hdmi 2.0 sockets to hdcp2.2 or something.
Best feature is definitely 3D I love it. Even use the virtual 3D feature which works brilliantly for games, cartoons and films with a lot of motion. Even ps4 and xbone games I put into virtual 3D mode adds atmosphere like fallout 4.