1. Ultimates lost a powerhouse but get a even smarter genius, FF gets a powerhouse and a genius who can apparently think outside the box
2. Superman loses an iconic back story but gets nice 4th world tech and maybe a refresher to the mythos, Darkseid probably becomes more focused on Superman then before
3, The X-Men get a respected Leader and a really good strategist
4. Don't see how Nightwing would benefit the Legion, but the Titans get a pretty powerful recruit
1. FF fall apart because the rest of the team contributes little that BM can't just do himself. Ultimates fall apart because they're trying not to be the Illuminati but have picked up an Illuminati member.
2. Superman gets fat because the New Gods do little aside from when Darkseid is pounding on the door. In those cases, Superman is involved the same amount as he is normally, because he's often involved with Darkseid anyways. Orion has already been a JLA member so this one's not hard to imagine. The JLA lose arguably their moral/de facto leader and gain the Dog of War.
3. Back in the day this would have been close to a wash. Nowadays, the X-Men win and the Avengers lose
4. Legion gains a (probably) better leader. Titans pick up a more powerful member. Hard to say beyond that.
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"And then there was nothing. A once broken something now void.
And on the first day, Doom spoke... 'Be.'
And then there was life."