I voted BerryzVsC-ute, All-Singles, and H!P Summer. Berikore was really fighting H!P Summer for that spot, though.
I went for H!P Summer because my love for Berikore stemmed more from the songlist and the performers than the actual concert production. I'm also a sucker for the H!P mix and match subunits too, and here they worked quite well. High-King! For more than one number!
Airi-Linlin-OgaSaki!
The summer theme was also more prevalent here than in the winter concerts, so the concert felt more unified, rather than "Our new singles! Some random shuffles! Special Generation and LoveMachine/RR21/ThePeace!". The costumes for the most part were pretty good, and of course the Ame finale was epic.(And the song hadn't been BEATEN TO DEATH YET.)
BerryzVsC-ute not only had a great songlist, but the subunit rosters were also quite strong, and I don't think there was really a "Make some great subunits(that made sense) and group the leftovers for a number" situation that seems to pop up in other concerts. The costumes were also decent, and the fact that the concert theme was something brought up again and again was very refreshing. More often than not the H!P concert names seem to be just tags, but here it was the driving force.
All-Singles had A LOT of production to match its epic premise. The medleys were mostly well-put together, and the solo distributions mostly made sense. The costumes were pretty good, too. And just the overall effort put into the concert on every front was so much that I couldn't not vote for it. I think it also set the benchmark for 9-nin MM 2.0. The extra work needed to cram 35+ songs into one concert really helped the lineup bond. The difference in the girls between BKBKB and Resonant Live is ridiculously apparent, and a completely different MM than in Sexy 8 Beat. And it seems lots of the good concepts from All-Singles were further explored in Resonant Live and P9D, extremely strong concerts. The medleys with changed arrangements, the generation-based MCs, etc. I find that production values for MM in general rose after this, with SYO and P9D having so many bonus treats.(They seem to be fading again, however.)