There's a book about the development of both of them, The Race for a New Game Machine: Creating the Chips Inside the XBox 360 and the Playstation 3 by David Shippy & Mickie Phipps. [0]

It has some details on the awkward position the IBM developers were put in.

Rodrigo Copetti's excellent articles on the PS3[1] and Xbox 360 [2]

and Ars' Hannibal's article on the Xenon Chip. [3]

[0] https://www.goodreads.com/en/book/show/6056634

[1] https://www.copetti.org/writings/consoles/playstation-3/

[2] https://www.copetti.org/writings/consoles/xbox-360/

[3] https://arstechnica.com/features/2005/06/xbox360-2/