Quick question.
I know that the AI is upgraded alot in BTS (unfortuently I can't play it because I have a mac ).
However, I've also heard alot of people around here say it's harder to get a win on emperor level in warlords then it is in BTS.
Is that true? If so, why is this if the AI is upgraded in BTS?
Well, it's both. The AI is "smarter" in BTS than in unmodded Warlords, but it also lost some its "cheating" bonuses, its bonuses to production, research, etc. have decreased. The reasoning being that it doesn't need them as much anymore because it plays better, and that improving the AI and keeping the bonuses would have been overkill. As to whether this has made the game easier or more difficult, my impression is that differs from one player to the next, you'll find many supporting voices for either claim, and it's hard to tell how it'll be for you before you get a chance to try BTS yourself.
The number of extra starting units the AI gets on high difficulty levels was one of the things that changed, it does not get more than one free worker anymore, this might be responsible for some high levels becoming easier than before because one additional initial worker of course makes a huge difference, and the smarter play might not be able to compensate for that.
I don't know if it works on Macs, but you might want to check out the BetterAI mod for Warlords, as the BTS AI improvements are based on it. So this might be a good way for you to get an idea about it.