I am a big burger consumer, and I tend to rank the various substitute burgers on a scale that indicates how satisfied I feel afterwards, and how accurate the imitation is.
I felt like the Beyond Burger was 8/10 in terms of being as satisfying as a burger, but only 6/10 in terms of being a good imitation.
For an example on why I use the different scales, plant-based patties tend to sear differently than real beef, tending to produce a thin crisp layer. This isn't great in terms of being a good imitation, but it actually has really good mouthfeel, so it increases the enjoyment.
Being 8/10 in terms of satisfaction is a pretty important threshold for me. It is at the level where I can eat one and feel like I ate a burger. Most veggie patties are in the 4-7 range (Gardein is pretty good) in terms of satisfaction, and even lower imitation quality.
When I first had the Impossible Burger a couple years ago, it was 9/10 satisfying and 8/10 imitation. It still had the distinctive plant-based patty crispiness, but the internal texture was much more accurate. This was back when the Impossible was only in a few dozen restaurants in the country, so this was at a nice place in Las Vegas. I got an Impossible and a Wagyu beef burger side by side for comparison. By the time I finished, the most obvious physical difference I'd noticed was that the Impossible burger loses heat much faster than a real beef burger.
In January 2019, Impossible began rolling out their 2.0 recipe, and they are now in hundreds of locations. I got the 2.0 at an upper tier burger place ($20 for a burger) and again did a side-by-side test. The Impossible still lost heat faster than a real beef burger, but the characteristic thin crispy sear on the patty was reduced significantly.
Visually, the inside of the patty was virtually indistinguishable from real beef. It's 10/10 satisfying and 9/10 imitation. I think it's indistinguishable from a Burger King quality burger, but still not quite as hot and juicy as a more expensive gourmet beef burger. I imagine they might be able to just make a less healthy version that is packed full of various oils and whatnot to get that quality.
Once the Impossible Burger rolls out to grocery stores later this year, I will never have to buy ground beef again.
To Beyond Meat's credit, their Beyond Brats are the best veggie sausage I have had, and as far as I know, Impossible doesn't have immediate plans to take on that market. I've found that they have supply chain/production issues with Beyond Brats, though, as they are almost always sold out at the Whole Foods near me.
TL;DR I believe Impossible Foods is going to eat Beyond Meat's lunch