Storage goes to the S8+ as it comes with default 64GB out of the box and has SD card to add more. Charging? Not sure what that mean but the S8+ has fast wireless and fast wired charging. Build materials and pretty even between the two phones.
Design would go to the S8+
Daydream is nice but so is the new Gear VR.....kinda evens out in that dept
Charging - Samsung is still using their "FastCharge" which is Qualcomm's QuickCharge 2.0 rebranded. The Pixel XL supports USB Power Delivery. It's just a more up to date and better tech. (most consumers will never care about this)
Storage - 128 is more than 64, both support expandable storage in the same quantities, one just uses the USB slot and the other uses a slot within the device.
Build materials - On that I just went with metal > glass due to durability, but both are using very good quality materials and both have excellent build quality.
Daydream - Only reason I brought this up is similar to charging. The Pixel is supporting a more up to date standard and the Gear VR, while for most people will be an acceptable alternative, it's not supporting the standard. (most consumers will never care about this)
Design is pretty subjective. I'd give it to the Pixel XL both functionally and aesthetically, obviously a lot of people would give it to the S8+ - As an example, I didn't know headphone jack on the bottom was a good thing, I suspect it's a preference thing.