128 , more future proof .
I always go for the biggest memory available. So it would be 128 GB. I tried the 64 GB and I only end up with around 30 GB of available space, which is enough but I feel like I need a bit more available space. With the 128 GB storage space. I have about 88GB of space left.
If the next iPhone comes with 256 GB and is at the same price, I might go for that.
The trouble is that the future is a new phone, not insufficient memory. I, too, went 128, but I see the folly of it every day. By the time I need more memory, I will long ago have upgraded the phone itself. Apple is seeing to that with iOS updates that slow down older hardware.