Neither. I use a good old fashioned Log in Notepad (thats right,
Notepad), filled with typos, intoxicated ramblings, and virtually no organization system whatsoever. I write in it a few times a week. I Love it.
But then again, it depends on if you want other people to read it. Personally, an offline log just works for me because I can write whatever I want without considering what other people will think. Because 90% of my what I write is utter garbage anyway. (and obviously, I dont expect people to read it) So I guess its more like a journal.
I think its the best thing to do for free form writing. Concentrate on the content, instead of how its delivered.
I can't stand twitter. I have never used twitter but I feel like anyone who uses it regularly is probably way too self absorbed.
Open notepad type .LOG on the first line, start typing on second line. Now it marks the time and date you open up the log automagically. Best tool for writing since papyrus.