Pay attention to your intuition, or just simply: What do you feel like using as a system? We’ve discovered people tend to resist the GTD® implementation process enough as it is, so you need all the help you can get to be motivated to work the system. If you know you’d like to be digital, don’t waste time on a paper system. But if you like the look and touch and feel of a cool notebook, go for it. No system works unless you work it.