I'm on the fence between the OnePlus 5 and the Essential phone, myself.
After owning a long line of Nexus devices, a OnePlus 3, then a Google Pixel XL, I made the switch to the Galaxy S8. Overall, the S8 has actually been great. But it does come with its annoyances, namely Samsung CONSTANTLY trying to push their proprietary apps through random weekly notifications and the Bixby interface. I've disabled a lot of the Samsung bloatware apps but the phone still lags/hangs more often than my OnePlus 3 or Pixel XL ever did, which is just sad. So I'm ready to get back into the more "pure Android" experience.
I was initially planning on holding out until the Pixel 2/Pixel XL 2 were announced but reputable rumors are consistently showing that the regular pixel will just have a 5" screen with huge bezels again and the XL 2 will be a monster of a phone with a 6" screen that matches the size of the S8+ but with even larger bezels. It will be pushing 6.4" tall, which is simply too big for me. So I've decided to look at other options. The reviews of the OnePlus 5 have been excellent and I was extremely close to pulling the trigger on one until news of the Essential phone really started to break recently.
These days I don't really root/mod my phones so that isn't much of a concern. And after experiencing the bezel-less life of the S8, it would be tough for me to go back to something with 2015/2016 size bezels. This is why the Essential phone really has my attention, at the moment. Plus the design of the Essential phone is very original and I love just about everything about it. However, I will admit that at least OnePlus makes good use of the large bottom bezel with the capacitive keys and finger print scanner. Not to mention that it costs over $150 less than the Essential Phone.
Personally, I'm having a really tough time deciding between the two. At least I've ruled out all other options, at this point.