Depends on what you want it for. If you want it for collection purposes then you should get the hard copy there's even a limited version if you want if you want to just play the game the digital copy would be better so you wouldn't need to carry too much games with you on the go if you go on a...
i think the last one i read was 21th century boys which i read after 20th century boys and i read alot of mangas that are ongoing cant even name them all
edit: no wait it was wakusei no samidare maybe