I prefer digital journals. Theyre more accessible for when you really need it and when you really need to get something out and are not motivated to move you can easily do it since most people always have their phones on them.
I'm a geek for well craft object and stationary no different for that. I prefer a handwritten journal because I develope a relationship to that objet, that fact that I love it's aesthetic, it's feeling to the touch, the color of the pen I chose. Those are things that make me happy and make me want to use my journal. It's was important when I started establishing this habit because I was excited to use my journal, and it's a part of my routine I enjoy. But that is very personal, a phone or a journal is as good if it makes you feel good. There's even apps that are beautiful and might make you feel the same way I feel about my journal. The most important thing I feel is to be consistent and have a way to keep this journal or e-journal for the years to come, and to go back in time and remember what you went through and how much you've grown.
I hand write on my iPad usually, but sometimes I do a regular handwritten journal or a completely digital app on my phone.
Sometimes I like journaling on my phone, if I'm running short on time, or if I'm in a situation where I cannot handwrite in my journal. When I have the time I prefer to write by hand, because I feel like everything comes out more easily and slower, so I can really see what I'm thinking more clearly.