Ok, so I have been informed that one of the best ways to record the live ambient sound of a live show for instance is to set two studio condensor mics in an X-Y stereo format on opposite sides of the room (L,R).
My question is this, should I have the mics really far apart on opposite sides of the room? Just because I read in an audio textbook that the mics should be next to each other in a crisscrossed fashion to mimic how ones ears would pick up the sound. This does make sense and would be easier (simply meaning less cable to lay down). I just wanted some expert advice.
If the mics are on opposite sides then they could possibly pick up completely different sounds (i.e. speaker placement, crowd reactions, sound bouncing).
But if there next to each other then it would be a biased recording, meaning it would sound specific to that particular location (where that person was "standing").
Just my opinion, I don't jack about sound recording, thanks for any info.

X-Y = CARDIOID mics right on top of each other pointed 90 degrees apart
A-B = OMNI mics seperated some distance apart

There are of course other options for stereo recording too, but those two are very common. You are kind of misxing the two a bit. If you seperate, then you probably would not point 90 degrees apart. You should do some searching on the net for stereo recording techniques to learn more, there is a ton of info out there. Thing with A-B is that it is not "mono-compatible", meaning if you have any chance that you want to mix the stereo down to mono, A-B is a BAD choice. X-Y on the other hand is mono compatible. And don't forget that A-B vs. X-Y use DIFFERENT types of mics, omni vs. cardioid respectively.

Here's a link to a page at Schoeps microphones that has an excellent technical overview of various stereo miking techniques and their pros and cons.

http://www.schoeps.de/PDFs/stereo-recording-techniques-e.pdf

Great thanks guys. So it is in fact narrowed down to X-Y and A-B. My guess is that I should use the X-Y since I was planning on getting a pair of Cardoid mics like these Rode NT-3's:

http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=233750&is=REG&addedTroughType=search

Seems like X-Y would be easier where I could keep them close by and monitor them next to me and a video camera.
Is this the setup/mics that you would recommend for my intended purposes. I certainly won't be using them in big arenas but more like local clubs and small concert venues which hold a couple hundred people. I just want to get the best sound/use the best setup for live bands. Thanks again for all the info!

Great thanks guys. So it is in fact narrowed down to X-Y and A-B. My guess is that I should use the X-Y since I was planning on getting a pair of Cardoid mics like these Rode NT-3's:

http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=233750&is=REG&addedTroughType=search

Seems like X-Y would be easier where I could keep them close by and monitor them next to me and a video camera.
Is this the setup/mics that you would recommend for my intended purposes. I certainly won't be using them in big arenas but more like local clubs and small concert venues which hold a couple hundred people. I just want to get the best sound/use the best setup for live bands. Thanks again for all the info!

You would not want to place X-Y or any other coincident stereo mics "close by ... the video camera." That's putting the cart before the horse. Position the mics for best sound pickup and proper stereo image. Period. Usually that will mean somewhere on a line extending from stage centre directly out into the audience. That may or may not be close to the camera. You position the mics for best audio imaging, the camera for best visual imaging. If they're the same general location with respect to the band it'll be purely by accident.