Well, the actual concert is about an hour and forty minutes on both the first and third dvd even though there are 60 extra some odd minutes of footage on the third DVD. It's been a while since I've seen the first concert (my friend owns that one, I own the other two) so I don't remember how the performances were all that well. I think a lot of them got tired towards the end, so there may have been more running around which I think made a couple of parts not so good vocally (but still great to watch).
The third DVD has no such problem and Melon sounds wonderfully for the whole thing. The solo and duet songs are fantastic. There's not a whole lot of bells and whistles during a Melon concert and what's listed on the DVD is what you get.
The MCs for the first and second DVD are pretty weird and they both have those weird movies where it becomes evident that Melon can't act. The third DVD's MCs are a little more normal with a (boring but short) poem for the first one (in both english and japanese), the second is Murata and Shibata doing stupid things to the olympics.
There are a couple songs that are sorely missed on the third DVD, such as Amai Anata no Aji, Skip, and ANNIVERSARY but I feel that the selection of Melon songs and the two covers are more than sufficient to make it a buyable DVD.
So...I guess I recommend the third one. It's a close call really, but the individual songs were a great way to showcase vocal talent and all the performances were stellar.
It's kind of funny how crowd surfing seems to crop up at a Melon concert. Not much, but it's there.
[And as a note, the concert DVD wasn't filmed at Chicken George (it's too crowded to shoot a proper idol concert) but Zepp Tokyo. You see some of the live house in the Natsu tour medley and you see it during the extras.]