Hi, welcome to this forum!
Well, Yoyogi has indeed more blocks in the center (1-6), while Yokohama Arena has only 3 (this I confirmed by looking at the seating diagram on the site of Yokohama Arena, and also by looking at many auctions). I believe that the B-row (and maybe C-row also still a bit), has still a good view. (But I don't know that until I'm actually there, but if you think logically about it, and that it's the same stage as last time, it'll have a good view.
I don't know about celga, how fast/slow they are. I always used akibado, they are a bit slow, but I kinda stick to them
About the current winnings on yahoo, well try to look at the auctions that are almost over. A-blocks are usually not under 40.000yen, B-blocks not under about 18000yen, and C-block at least more than normal ticket price (which is about 8000yen). For tickets not in the center (so アリーナ), they variate, and you'll have to check the yokohama arena site for the exact location of the blocks.
And then there's always the last option of the reseller shops

(for the second concert

)
Cya!
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My Japan Blog (and about Ayu, Anime,Figures,...)
Japan 2007 Trip Travel Blog (May 4-18,Ayu Concert x2)
Japan 2008 Trip Travel Blog (March 23-April 08,Ayu,gazette,X-Japan Concert & Tokyo Anime Fair)
Japan 2009 Trip Travel Blog (April 26-May 13,Ayu & Perfume Concert & Dolls Party 21)
Tokyo 2009 (Dec 27-Jan 3, Ayu CDL Concert)
Japan 2010 (April 6-23, Ayu & Kuu Concert?)
January 28th 2010: The day everything changed for international Ayu fans. <3