Generally speaking, with regards to “4K” (today’s 4K and not yesterday’s 4K or the 4K before that, or the one before that)…
4K (Ultra, Mega Ultra, Mighty Stupid Insane Mega Ultra) is still a moving target. And ATSC 3 is coming, so even more changes that will make you throw away your $80K laser projector (exaggeration).
My point, if you need a 4K TV now, I’d plan on something you’re “ok” replacing in 2-5 years. In other words, if you’re a 7+ year person, changes happening in the next year or two or possibly three will begin to frustrate you. IMHO
I own a (can’t buy this anymore) 1080p OLED TV. Why? For the reasons above. Timing for all of this couldn’t have been worse. I mean, they are forcing everyone to buy a 4K TV and if yours isn’t already (roughly) obsolete technology wise, it’s going to be. And that really hurts when you have the advent of technology like affordable OLED, affordable being on the high end fringe of affordability for most. Most people want the “best”, but the best isn’t really achievable when the target moves from year to year (that is quickly).
If you have the cash to burn, get an OLED. You’ll love it. And in three years, I’m sure you’ll love the OLED you will replace it with 
My OLED already has over 2 years of age on it. I won’t be feeling nearly as much pain when ATSC 3 becomes the thing everyone wants (noting it also means a new Tablo device, and there’s nothing saying that will cheap in any way) in two to three years.
If I were forced to buy now, I’d buy a reasonable cheaper LED/LCD TV so I don’t feel quite as sad chunking it in a few years.
With that said, there’s nothing saying that the wave of fast paced changes is about to stabilize in 3 - 5 years. It might not… then of course, we’re all sad 
Not trying to paint a really bleak picture. But it certainly helps if you’re comfortable spending a couple of thousand on a device that might frustrate you in as little as 3 years. Otherwise, I’d probably play it safer and go with a more affordable TV and do a bit of waiting yet. You know the world changes for sure post ATSC 3.0 (and again, it will mean a new Tablo as well).
If you can wait, wait. If not, hope you get something you can live with.
(I really like my LG 55eg9100 TV btw, more than enough for my house. I paid $1300 new, over two years ago. Set is on for at least 12-14 hours every day.)