I've read most of the Buffett books, and I've been tracking this one for the last couple years. (My copy should be here in the next day or two.) I've read through a couple dozen reviews, and these are simultaneously the most detailed yet snarky summaries I've seen:
Warren Buffett Snowball Review - Executive Articles - Print - Portfolio.com
Buffett Snowball Review Part 2 - Executive Articles - Print - Portfolio.com
Buffett Snowball Review Part 3 - Executive Articles - Portfolio.com
Buffett Snowball Review Part 4 - Executive Articles - Print - Portfolio.com
Buffett Snowball Review Part 5 - Executive Articles - Print - Portfolio.com
Of course I'm a bit biased, with my opinion being that the only debate would be whether you pay money for the book now or wait a few weeks for the library to stock it. Yes, I shelled out a whole $19.25 for this privilege...
I think that in 5-10 years Alice Schroeder's effort will be viewed as the most thorough-- practically a Buffett concordance-- while Lowenstein will still be recognized as having written the best overall Buffett biography.
One interesting sidelight that I've only seen mentioned once: Schroeder spent so much time with Buffett and interviewing his family & friends that she realized her own marriage was doomed. She and her husband had been trying to work out their differences, but as the two of them got to know Buffett and saw how he treated the people around him, they both realized that they'd never reach consensus. They divorced more amicably than would have seemed possible.
I sure hope Lowenstein is writing a book about the real estate and credit meltdowns. I've enjoyed his research & analyses of other financial disasters.