Plus all-in-ones usually contain laptop hardware. So its better off spending on the laptop to get the portability. All-in-ones will never have the same performance as a desktop.
I completely agree.
All-in-ones are here to stay, but once something goes wrong it can be a hassle. If you are a non-gamer I'd recommend something like an ASUS laptop with a quad-core APU and buy a separate desktop monitor.
You don't need to use the laptop monitor but you could use just the laptop screen, the desktop screen or BOTH.
Non-gaming desktop computers on the other hand contain a lot of empty space, nor do you get the potential portability of the laptop or even its battery in case of power failure.
The advantage of the desktop is that you can repair it easier and add more hard drives than laptops. However you can buy USB hard drives and laptops aren't that prone to failure anymore.