I am actually not too sure if it is the Screen Resolution or the EMUI9.1 optimizations that are giving the P30 Pro it's great battery life.I was a little surprised how easily I noticed the difference because I always used the S10+ in the same FHD+ mode. Not a deal breaker though and no doubt helps give the P30 Pro it's outstanding battery life.
The new EROFS File System has give the P30 Pro quite a performance boost over the Mate 20 Pro, but we will need to wait until the Mate 20 Pro gets EMUI9.1 to confirm, hopefully I will still have both devices to give a thorough comparison.
Each time I use the Mate 20 Pro and then come back to the P30 Pro I am shocked at how much more fluid snappy the P30 Pro is, yet they are both on the same Kirin980 SoC.