I used to read physical copies of manga. Then I had to move and a someone had the bright idea of putting my boxes of manga by our fishtank. Long story short, I no manga now.
I had a similar experience with a flooded apartment and some boxes of comics. I have felt your pain.
BTW, I prefer physical copies for home sofa reading and digital for traveling (though a Nexus 7 screen is still too small for American comics pages). Physical copies will eat up your shelf space if you read more than one series and/or do not cull the collection. 20th Century Boys is 30 volumes of manga.
I definitely prefer physical. While digital is more convenient (and in most cases, are of higher quality depending), I'd prefer not to stare into a light if I don't have to.
I also feel better when the manga I'm reading is printed on quality paper too, and doesn't deteriorate fast -GA Geijutsuka - Art Design Class' volumes are printed on excellent quality paper.