Sure your points are valid about avoiding printing on public printers but the problem with writing such data by hands is that it is prone to errors. Humans make errors. Even copy-paste is not error free, you may paste some different data than you intended or skip a digit, but hand writing?
You know I had a cold storage once that I created by copy-pasting some data around, and when I was to recreate the wallet to "hot" it was an experience full of stress, I was not sure if it will work out as I intended. If I had had it manually written down, I would have been freaking out (!)
So if it is a nice sum of money, I wouldn't hide it behind a handwritten private key. Private key is long and we are only humans!
I really stand by my previous advice of using a hardware wallet to protect your money. And if it is a large sum, than: all the more