One of the reasons I've traditionally preferred Chirpstory over Storify is that Chirp has always let you move large amounts of tweets at once (50 at one go). I've just noticed that Storify now lets you move 20 at one go - I don't know how long this has been possible, only visited the site today.
Anyway this is the bit to look for, highlighted in green.
For big events with lots of tweeting I'd still go for Chirpstory - another advantage is that you can re-order the tweets so that the earliest is at the top. You can also easily remove duplicates (which can creep in if you go back and edit on the second day of the conference, for examp, adding in the more recently posted tweets).
More Twitter wrangling tools here: http://brodiesnotes.blogspot.co.uk/2011/05/list-of-tools-for-finding-or-capturing.html