Difference between regions?

[CSD]

I have a PAL PS3, which means I have to check before buying any region A blu-rays. It also means that I can't pre-order any movies and must wait until after their release to verify that they're region-free.

I'm thinking of just avoiding it all by buying region B discs and be done with it. Another thing is that region B discs have Arabic subtitles, which my best friend appreciates.The problem is, how do I find out if both versions are identical when it comes to additional features? I'd rather wait for a region 1 disc than get a region B disc with less extras.

For example, I want to pre-order the region B version of Iron Man, but the description and picture found on Amazon UK shows only one disc, while Amaon US shows two discs.

What's a reliable site I can use to find out about any differences between the two? And are the two regions usually different?

Thanks.