Chris, Great job on that review.

You beat me to it! Glad for your early release, thorough look at these two prime contenders.
One thing I like about the new ThermoPro Lightning is the way the probe is more protected when the probe is closed. I don’t know how much difference this will make, but it does show some new and creative thinking.
My main comment would be that Thermoworks is clearly the consistent provider of high end, temperature products at premium - but well deserved - prices. A great company with a great reputation.
ThermoPro, on the other hand has had to get a foothold by offering decent products at amazing prices by combining Chinese manufacturing and the Amazon shipping and marketing juggernaut. Since then, however, they have been working hard to be taken seriously as a legitimate company selling good products - not just more of the many badge-engineered dubious thermometers offered on Amazon by companies with sketchy names and no customer support. This shows most clearly by the warranty they offer and the mostly positive accounts we have seen by members here who have had a customer service need.
In a way, I think that ThermoPro has taken a page from Harbor Freight. They, too, started out competing almost entirely on price. But now HF offers some substantially improved product lines that are knocking at the door of the major quality brands from big box stores. ThermoPro’s products have gotten better and better, narrowing the quality gap for these instant read thermometers. The TP-19H is still the best overall value out there in my opinion. A decent, pretty solid device that is more than adequate for most needs. My wife has practically appropriated mine for her kitchen use.
ThermoPro TP19H Digital Meat Thermometer for Cooking with Ambidextrous Backlit and Motion Sensing Kitchen Cooking Food Thermometer for BBQ Grill Smoker Oil Fry Candy Instant Read Thermometer
https://www.amazon.com/dp/B07XXSYLL8/?tag=tvwb-20
Since then, they tried to raise the bar with the TP-620 with a bright LED display and anti-slip sides. A very nice thermometer, but I use both and when compared directly to a Thermapen One, it comes up short.
ThermoPro TP620 Professional Thermocouple Instant Read Meat Thermometer, Ambidextrous Backlight LCD Kitchen Thermometer with Motion-Sensing, Digital Food Thermometer for Cooking Smoker BBQ Grill
https://www.amazon.com/dp/B08BC9KF45/?tag=tvwb-20
So now comes this Lightning. It seems from your review (and Tom Horsman’s less thorough look) that the differences have narrowed considerably. I think it’s coming down more to what a person happens to like. Both the Lightning and the One would make great choices. The relatively small differences in features might spell out which one someone chooses. Would you rather have a bright red readout or a backlit one that can rotate 360 degrees? Both are valid choices in my book.
Going back to the companies themselves, I do respect Thermoworks for using European manufacturing, and their overall reputation is practically impeccable. But, again, ThermoPro deserves to be taken seriously as a competitor and not dismissed as another cheap knockoff rebadger.
p.s. Chris, I do agree that ThermoPro went too far in the “comparison” advertising. The specs they aim at read like products from one of those bogus “companies” on Amazon while the pictures they use are clearly intended to evoke a Thermapen. On the other hand, I have seen a Thermoworks ad putting down competitor products as cheap but not distinguishing a credible alternative like the Thermoworks TP-19H from junky no name products proliferating Amazon.