So here's my take on this discussion. I have a Google pixel 2 XL and my wife has a OnePlus 6 (not T). I bought the 2 XL because of camera, but since there has been software updates and even XDA developers making it possible to have better cameras on other phones, Google pixel 3 is looking like it's going to have a tough time. My pixel does not keep apps open and hates multitasking, has much less options for gestures and shortcuts, and I love how the OnePlus 6 has the sound, silent, and vibrate slider (like the iPhone, but add a vibrate to that). The notch is also almost non existent cuz you can turn on or off the notch in settings and pick which apps you will allow the notch to be on (default is off on all apps). Sure the screen is fhd+ and not QHD but that is insignificant if you compare the two. The OnePlus also gets brighter, battery lasts longer, UI is smoother AND faster (and I have mine set to .5 animations), it also charges insanely fast. Comparing the two is like a beast (OnePlus) vs. software AI (which OnePlus is catching up to). Google does have unlimited photos (which is a great point btw), the 3 has wireless charging (also great), but doesn't really work with other fast chargers???, Sure it has IP rating, but the OnePlus can get wet (tests on youtube, you can look it up, it's also on their website as splashproof). I would prefer dash charging any day because it's ridiculously fast, OnePlus also has THE best UI I have ever tried (tried iPhones, Samsung, Nova launcher, LG, sadnly no chinese, HTC. It is soooo goooooooooddddd). And UI experience IMO is very important, and as an Android phone, so is multi tasking, which all Google pixels suck at. I can manage 3 windows/apps before having to relaunch an app on my pixel, I've tested the OnePlus 6, kepps apps all open, fast, smooth, worry free.
So on the upside to Google pixel 3, it has that wide angle selfie lens, the top notch picture selection, great wireless charging (with the Google pixel stand), unlimited photo storage, front firing speakers, hopefully the Google AI auto answering and setting appointments (I really hope this happens sooner than later). That's about all I can think of that the pixel would be different from the OnePlus 6t or any other phones.
TL

R OnePlus is faster and smoother and keeps apps open.
Google pixel 3 has wireless charging, unlimited photo storage, wide angle selfies.