To me, Manga can be, or actually is like reading a really interesting book.
I like turning a page with my hands and reading it, maybe it's because when I was growing up, it was a time before digital was used this much...
I like them both, but if I had to choose I'd really like a printed one, something I can feel in my hands. I just seem to cherish it more than something stored on my laptop...
I mean, I collect a lot of manga in my room and I just cherish it more than the few hundreds of GB worth of manga/doujinshi on my laptop. (not to say I don't, just comparatively)
Digital is pretty convenient, but when I go somewhere without either 1) electricity 2) internet or 3) my laptop
Mostly when I travel, I can't access it. Stuffing a book/manga into my bag and just pulling it out is easier. Except, well, I don't have access to as many.
But definitely one of the biggest things is...Not every manga is available online, or in digital form.
Some very rare, Out Of Print stuff I have, I can't find online. Some commissions I receive don't have digital versions either, and I have to translate off a physical copy, which is fun too in it's own right.