Blackest Night feels kind of predictable to me, with a lot of treading of water going on. I dropped the main series with #5, and from what I've read of #6, I'm glad I did so.
Dark Reign, however, I've been exposed to only in the form of the titles I read regularly that it's happened to crossover into. I haven't bothered with any of the minis or new series spinning out of it. From that little exposure, I've found it to be decent, but not really on the level of a full-scale event.
I'm more interested in Siege than anything, but with it just getting rolling, I don't think it's fair to compare it to Blackest Night.
So at this point, neither.