Back in the days of 720 v 1080, I remember reading an article by one of the companies that made a living testing and reviewing electronics. They took their staff and had them watch 50" tvs at normal viewing distances in 720 and 1080 resolution. The conclusion was the folks whose job it was to review TVs for a living couldn’t tell the difference at that sized set (or smaller). Several years later, 4k is all the rage. Seems to me it could make sense if you are going big 65" or larger) or sit closer than normal to the set. But at this point, 4k is pretty cheap. 3D was all the rage a couple years ago. Not something I see advertised much lately. OLED is better (and more expensive). For that I would look at whether you can tell the difference (my wife watched non-HD channels for years when those were still available because she couldn’t tell the difference or at least didn’t care enough about it). If you can’t or don’t really care or don’t watch TV/movies much, probably skip OLED.
4K: Most good quality TVs will have 4K capability, so you don’t really have to splurge much to het that. Most of the 4K TVs will support HDR which can provide more accurate colors and arguably makes more of a difference than you will notice going from HD to 4K. You’ll find shows on Netflix and Amazon Video that now support HDR. iTunes and Vudu/Movies Anywhere now have 4K movies and the streaming quality is excellent. It’s good enough that we no longer see ourselves buying discs anymore.
Re paying a fortune for cable: Depending on how your cable provider charges for bundles, consider a streaming service such as Directv Now, Hulu, Playstation Vue, Sling, or YouTube TV. For $35-40 per month you can get the majority of channels that you are likely to watch on cable. We’ve done that for over a year and saved a lot because our cable provider won’t bargain anymore after the promo period is up. Many of those streaming services will have deals where you can get a free streaming device like a Roku, Amazon Fire TV, or Apple TV if you sign up for a month or 3. If you don’t like the service, you can use the device with a different service. Your new TV may even have one of the streaming services built in, likely Sling.
A good overview of what is available out there as far as streaming:
https://www.seattletimes.com/business/heres-the-skinny-on-streaming-tv-options-for-cordcutters/
No it’s still the case that the cheaper led tvs don’t do so well with sports. I bought a cheap Samsung and it isn’t as good as my expensive Samsung.
The smart tvs are great, we don’t use much. Maybe once in a while to watch Netflix. You’ll still need reliable internet and a good wireless or even wired connection.
I must be the last cc person who had the 25 year old, 200 lb, 25" deep, wood console Zenith tv…that would NOT die…
Thankfully we moved in January and I refused to take it anywhere but recycling. H went to very small town Walmart and bought a Vizio an hour before playoffs began. Works great! Should’ve gotten a bigger one, but anything was an improvement 
We used to have a 30-something inch boxy TV for almost 16 years and would not buy a new one when LEDs and plasma became the rage. Kid drew a sad face on a piece of paper and wrote “puny, sucky television” and taped it to the TV to shame us into buying a new one… she succeeded. It was not that long ago. Now that TV is too dumb!
@BunsenBurner I like your kid’s style! Haha
Consumer reports just did a TV issue. We are very happy with the 55" Samsung UN55MU800DFXZA we bought at Costco. Currently it sells for around $680. Great picture for a mid ranged model. It has a connection pod linked to the TV by a single cable where you plug in your HDMI devices and optical out. It also has ‘effective’ HDR (basically a brightness measurement) which is better than the low end series, but not as good as the LG OLED TV’s, which sell for about 2-3x more.
The ‘smart remote’ that comes with Samsung TV’s is a pain to setup with infra-red devices, like the Sonos sound bar we have (it uses radio). Best streaming results are with a wired Ethernet connection.
Sound is not great on any TV, just add a soundbar.
Thanks for all the advice. H remeasured our space and decided that we could fit a 65” in our space.
It was an extra $250 to go from the 55 to the 65 so we went with the 65”.
Got a LG super UHD smart tv. It has all the apps built in and a sling box (whatever that is lol). The store said this is their most popular tv and they can’t keep them in stock. It’s still in the box so I can’t say how it looks but I’m sure I’ll be happy.
For someone who is on a spending freeze, I have spent an inordinate amount of money this past week.
@deb922 , you said the treadmill AND the tv were prompted by your H - you haven’t spent a dime on yourself!! 