thats exactly what i was looking for!! will u recommend s9+ over one plus6? or p20 pro?
For software updates, I'm just gonna say this applies to all 3 phones you mentioned. The S9, OP6 and P20 are each of the manufacturers first phones with Project Treble, so I'm not sure how update delivery timelines will be affected.
Hopefully they'll be quicker, but OP6 for sure will be the quickest to get Android P out of these 3 because it requires the least work. Followed by the S9+ and then the P20 Pro getting it last, because Huawei is the worst with software updates.
For camera, probably P20 Pro, because I've heard nothing but good things about its camera. S9's dual aperture is a good feature with a lot of potential that Samsung isn't fully taking advantage of because of their lacking camera software. Not sure about OP6 camera, haven't used one and haven't watched any in-depth reviews.
For battery life, my S9+ gives me great battery life. Easily lasts a 16-17 hour day with around 6-7 hours of screen on time and still 30% remaining.
P20 Pro has a 4000 mAh battery, so you could probably get like 2 days out of that thing. Keep in mind, the way it achieves good battery life is because of its somewhat aggressive app management. It tends to close apps in the background very quickly, not only to save battery, but free up RAM as well. This can cause apps constantly relaunching and possibly delayed notifications.
OnePlus' kernel tuning will give you consistently good battery life and they have some nifty features built-in to improve battery life so I'd say all 3 phones are good performers when it comes to battery. However, using dash charging regularly on the OP6 will wear out the battery quicker, reducing battery life quicker than the S9 and P20 Pro.
Performance wise, OP6 on top. Without a doubt.
S9+ coming up in second place and P20 Pro last, because of the aggressive RAM management I mentioned above and because EMUI is a mess.
Display, I think we all know who wins in this department...
hint: it starts with S, and ends with 'amsung'.
Want a good all rounder that will last long? OnePlus 6.
Want a phone that will last you 3 years and then start to get frustrating? S9+
Want a phone that will just look cool and have 3 great cameras? P20 Pro.