E-copies are great if you have very limited storage space. Also, you avoid postal costs and/or travel costs. However, there's a chance of occasional drive failure and they're useless without power.
I buy the physical copies since it forces me to get some exercise walking a mile to the nearby comics superstore. When I'm at the superstore, I can browse other material: comics, books, toys, models, videos, etc. I then have to walk another half mile to reach the nearest Underground station for the journey home after work.
I used to buy multiple covers but then realised that this was pointless without a high level of collecting zeal and/or a good resale value. I got rid of my excess multiples and now my Transformers comic collection fits into a single, moderate-size cupboard. I have nearly all G1, Dreamwave, IDW and Skybound.