No idea if you’re getting Android or iOS, I’ll guess Android. I honestly find anything lower than 8GB to be too little for Android these days, but that’s mainly because I play games on my Android devices. If you don’t play games much, 4GB is probably fine. Something like Genshin Impact won’t run well on 4GB, even Arknights runs noticeably slower. Just for YouTube or texting or whatever, 4GB is probably fine.