The Samsung Galaxy A8 is a newer phone with more recent features, such as a dual-lens front-facing camera, an IP68 water resistance rating, and Samsung's Infinity Display. However, it has a mid-range processor and may not perform as well as the Samsung S8 Plus Edge in terms of processing power and speed.
The Samsung S8 Plus Edge is a flagship phone from 2017 with high-end specs such as a powerful processor, a large display with a resolution of 1440 x 2960 pixels, and a great camera. However, it's important to consider that it's a second-hand device and may have some wear and tear or potential issues due to its age.
It depends on your budget and what features you prioritize. If you're looking for a newer device with a more recent design and features, then the Samsung Galaxy A8 may be the better option for you. However, if you're looking for a more powerful device with a better camera and don't mind a second-hand phone, then the Samsung S8 Plus Edge could be a good choice.