In my case, I have two discrete systems. My work system is in the company-sanctioned Outlook, and my personal system is a hybrid of paper & Evernote. I've done paper for both, but it's just so much easier to drag emails into Tasks in Outlook than set up a bunch of email-based folders and write the task on a paper list... It really depends on your average turnaround time and level of work, I think. My work is predominantly administrative (at the day job) so quick turnaround and drag-and-drop work for me.
My personal is another story, and has a number of different components that I won't go into here. I'm currently experimenting with a combination of paper/digital. I typically go back-and-forth between all paper, all digital, and a combination thereof. And I'm OK with that. If I'm in a particularly tactile frame of mind, there's nothing like paper. If I want portability and quick review, I go digital.