Guys -

Help me out here. I know there's an article that goes over the AI's research preferences in detail, how much value it assigns to each tech, etc. etc. Where is it? I've been searching for it but just can't find it!

well it depends, in the xml file you can see something that shows what each leader favors(isabell obviously favors religion) and depending what they favor depends what they go after

Great people research preferences:
http://forums.civfanatics.com/showthread.php?t=140952

AI leader preferences:
http://forums.civfanatics.com/showthread.php?t=161282