OLED has the best image quality on the market and LG is the one making the panels for both Sony and LG, so you can pick either. The Vizio P Quantum is well reviewed as well. But, from my limited reading, is only available as a 65" display. You go down to the standard P series if you want 55".
55" is pretty darn tiny by most standards these days, but if you sit 6 or 7 feet away, it may be perfect for you. If you are further back, I would try to get something larger. Maybe a lot larger.
I would get the LG for sure, but be aware of burn-in potential which LCD does not really have.
If I were going LCD, then I would probably go with the Sony XBR55X900F 55-Inch 4K Ultra HD model...
https://www.amazon.com/gp/product/B078GWPQRB?tag=rtings-tv-bm11b-20&ie=UTF8&th=1
I mean, I'd have to scratch up the money to get it in a size which compensates for the rest of my life, but yeah, 55" is available as well.