Been thinking about this a little bit more.
Do I really just want to copy the files over? What happens in the future when the disk is full and I need to go back and remove some files, that I deleted a few months previously on my work disk. Looking through 500gb of images is not going to fun.
I think using the synchronization software from Microsoft might have its advantages, although it will be slower and I have to put more time into running the program, but it means the backup disk is not full of discarded images. Saving me time and space in the future.
I seem to have done an about turn on this, but I think it makes sense. I'm still going to keep robocopy, as it definitely is a useful program.