Mine is 1520 updated to 8. 1 and the system is slimmer. In fact, the mobile phone traffic is not smooth, the key depends on how you use it. Nokia and iphone are both good, iphone system is more mature, and 1520 is more atmospheric. Anyway, the mobile phone is very smooth After all, wp system doesn't eat hardware, and many iPhones used by my friends are also good, and some of them are stuck, which varies from person to person. The wp system will definitely get better and better. After all, it is just starting, relatively novel, but not perfect, but the commonly used software is absolutely satisfied. Iphone belongs to arcade, which can be seen everywhere on the street and is popular in the mainstream. See what you like.