Samsung is giving me the runaround with the 512gb model. It was supposed to ship today. I have been away from android for awhile. I initially had the 128gb but returned it to T-Mobile for more memory (obviously). In your guy’s expertise would you go for higher memory or just add an SD card? I thought in the past and correct me if I am wrong SD cards slowed down android phones. Again been awhile since I made the jump back over. Thank you in advance!!