How do you decide when you are writing whether you are better off doing so via paper and pen versus writing it into a Word document, or some other digital medium?

For whatever reason this question always leaves me feeling conflicted, and after a couple of minutes into my reasoning on the subject I've already contradicted myself. There's obviously not a right or wrong answer here, but I'm curious what other people's thought on the subject are.

I have reasons for preferring both, but my reasons don't seem to offer too much in the way of a good rule of thumb. But anyway, here's some of my thoughts.

For me working with pen and paper is a great way to start working on a problem. There's something about using pen and paper that helps get my creative juices flowing. It's easy when writing via a keyboard to erase the first words you put down, but with pen and paper this is more difficult so you're forced to stick with what you got for now, and worry about editing it later. This forces you down a linear path which is much more akin to the way our brain works, rather than the endless options in a digital format to erase and redo.

Ok, back on topic. If I write something with pen and paper I notice I remember it much better, perhaps because it's a slower process and it's more physically involved. But this is the same reason that I dislike it. Once I'm into the flow of an idea, it's coming from my brain faster than I can write.

The other area pen and paper loses out is in storage. Once you have it on paper it needs to be physically stored. Ideally you have it in a notebook with other similarly themed ideas. But if you're not that organized you end up with a notebook full of all sorts of different stuff that may not be related.

If you are storing in digital medium, it matter less that you are unorganized because you can use Google Desktop or Microsoft Window's search to look through all the files on your computer to match what you are looking for. There's some hope you can get to the idea from a year ago just by remembering a few keywords.

In a perfect world there'd be a really great tablet pc device that I could use to emulate my attachment to pen and paper to start working on an idea, or to jot down a to do list, but then I'd be able to convert that into digital text that would be searchable for future reference.

Anyway, does anybody have any sort of system for how they deal with these problems, or am I the only one that perceives them as problems?