I think both groups have been working really hard during these past years, and I, as a C-ute's and Momusu fan, don't think don't think anyone can deny that. Berryz have put all their effort in what they were doing, I don't now why they should be questioned to have a budokan live.
I think the issue here is the way Tsunku made the announcements, making it look as if he was doing a favour to berryz. And that's why it looks like it was a reward for C-ute and he was forced to give it to berryz too, but what if he had done it the other way round?
Would be even worse maybe? C-ute selling out their tour shows has been known since last year, and the girls has been sending clear message to the fans and the management that they want to go to Budokan. If at that point the Budokan show was given to Berryz instead of C-ute who have expressed their intention very clearly, I imagine fans would enrage, with probably something like unfair treatment and such. People will question the same thing as now about what Berryz has done that they deserve Budokan more than C-ute. And when they finally announce C-ute's Budokan it would be credited to the company bowing down to fans rage instead of the groups own achievement. It's pretty frightening to imagine tbh..