Hm...seeing Aztechnology fall would be interesting. Being able to run in Mexico would be nice, because as it is, Aztechnology has too tight of a strangle hold on the nation to make it feasible for runners. But at the same time, I really really like them as boogey men. And them having their own nation does help keep them mysterious and more dangerous than the other megas.
I don't know what makes Renraku special anymore. What have they done since their CEO kicked the bucket and they led to the events of Crash 2.0. Seeing them go would help shake up the setting.
I like all the other megas. I'm not in love with Saeder-Krupp, but we need a mega corp with a dragon CEO. That's pretty much what separates Shadowrun from normal cyberpunk. In fact, I'd like more crazy drek like that, like an AI, Sasquatch, or free spirit CEO, or something weird like that.
I like Horizon, because its very modern cyberpunk. Treating people like literal interchangeable cogs, being metrics driven, personality cult, it's wonderful.
Wuxing, I want more about these guys. I like the idea of them being dangerous by altering ley lines with geomancy and such. But I want more.
I also like the internal politics of Shiawase and Ares. Though, Ares has taken a very interesting turn by playing with forces they shouldn't have. But that's awesome. That's so fitting for the setting.
EVO falls under the same reason I like SK, for just being uniquely shadowrun. A mega corp all about making products for trolls, orks and dwarves, with a free spirit on the board. You can't do that in any other setting. Also, they're transhumanist agenda is also very post cyberpunk and helps keep Shadowrun from feeling dated.
I like MCT for their yakuza mega corp gimmick, but I wouldn't be against seeing them go.
So, I'd either vote for Renraku or Aztechnology. Not sure which way I'd lean just yet.