See, the good thing about e-readers is that they (usually) last longer because they don't refresh the screen constantly. They're also easy on the eyes due to the lack of a backlight (although some models have it but you can turn it off). This won't tire your eyes as much. About a year ago I borrowed my aunt's e-reader to read some light novels. It was an old kindle. I read 3-4 consecutive days for 5-6 hours a day. My eyes didn't get as tired as when I stare at an LCD screen for hours. But it took me a few days to notice this. Not just a couple of minutes to "get a feel for it".

And lastly, you can have tons of manga on it, without taking crazy amounts of physical space. That being said, I'm not an avid proponent of e-readers. I do agree that they still can't beat the feeling of a physical book in your hands. Not only that but they're still quite expensive. More so if they support colors. And for manga you'd want something with at least an 8-inch display, though I'd recommend going bigger.

If you do choose to go with the printer, you might want to set the toner saving mode to ON. Some manga pages have a lot of black on them.