Another vote for MacDive - the developer is amazing, he responds to emails within minutes, have used it for years, and I sync it with my phone so I always have my complete log with me wherever I go.
I am a data junkie, and I spend a lot of time writing up my dives. This is far easier with an electronic logbook, I can type long descriptions of conditions, supplemental information about the site, etc... Also, I usually do most of my commentary when I have Internet access, often you can get a lot of good information about a dive site online that you can incorporate into your own journal. If I'm on a long dive trip away from my laptop, I do make some paper notes but then I use them to complete my log as soon as I can, with data from my dive computer.
I don't really understand the use paper logs these days. So scary to think about all that precious information being lost forever, so much better to have all of your data with you all of the time, just so much more convenient to use a computer log.
There are only 3 reasons that I can think of for using paper:
1) The concern that an instructor or dive charter would want to see a physical log - I hear that a lot in these discussions, have never encountered anything like that myself, maybe an urban legend? If I ever needed a paper log, I could print out a very detailed on in minutes. Can't imagine that not being adequate, but I guess anything is possible.
2) Buddy signatures. My phone log can actually record a signature, I never use this. Not sure what the point is, or what the legal issues are. I can't imagine a situation where you would want to do a dive or training and someone would say that the electronic signature is no good. Seriously, these aren't legal documents. It's not like you have them notarized - if you wanted to fake a dive log, you could just fake the signatures as well.
3) Stamps. Some people like the stamps that dive operators give out. I guess if you really want those, and don't want to scan them into an electronic log, then you should use paper!