So, I've kept hold of both the Mate 20 Pro and Pixel 3XL and have been testing while I've been out in Silicon Valley with work for the week.
The Mate 20 pro battery is amazing along with the fast charge and I've really noticed the difference, I've also learnt by default that the Mate 20 pro screen is set to a warm look which makes the screen look worse. I changed this to a more neutral tone and changed the colours to vibrant.
I'm now really happy with the screen, get a slight green glow on the edges at certain angles when the phone is tilted, I think this is down to the curve. I haven't seen anything like people have shown on the internet.
For me the only reason to use the Pixel 3XL is the camera, I've been doing more testing with the Mate 20 Pro vs the Pixel 3 and they are really close. The Macro and 5X Zoom on the Mate 20 Pro are great.
For me, the Pixel strength is in the selfies and portrait modes, it's hard to get the same quality with the Mate 20 Pro. The pictures have an airbrushed look to them and also makes the subjects look pale. For day to day snaps I believe the Mate 20 Pro take the better picture but sometimes you need to put a little bit more in an persevere with the phone, I've been doing a lot of side by side comparisons and the Mate 20 comes out with slightly more detail.
I also prefer the night mode on the Mate 20 Pro , the Pixel looks almost artificial in comparison when it comes to the lighting and shadows and I have seen a lot of noise in certain pictures.
Update wise, it remains to be seen how good Huawei will be, no way they will be as good Google but I'm hoping with Android 9 and the separation of core google apps from the OS makes this better.
There are also a number of strengths like screen recording which is cool, I'm using action launcher over the top so for me I'm not experiencing any of the challenges with the default skin. Only issue is sometimes you can't quickly switch between apps in the task launcher without bringing the app into focus i.e. if it's off to the left on the task switcher you have to bring it to the centre before you can select.
Overall I'm becoming happier with the Mate 20 pro everyday and seeing less reason to use the Pixel 3, I will carry on with both for now and see how it pans out.