In order to differentiate themselves and win more business, the three largest online travel booking sites are introducing new features and offering more information.

While no one site is uniformly best, and travelers often check more than one sites before booking, each is trying in their own way to offer products that consumers most want.

In my own experience, Orbitz consistently finds the best fares on complex and last minute itineraries. That isn’t because Orbitz has the best agreements with the airlines that founded it, either. It’s because Orbitz has the “best math” — the best search functions that are able to piece together flights that the other sites don’t think of. I’ve often found cheap flights on Orbitz that other engines couldn’t find, and then picked my flights one by one on Expedia only to find the same price (or even a few dollars lower). So Orbitz is a very useful tool.

Of course, consumers have already figured out that it’s best to check more than one distribution site. Since the sites have access to different inventory at different times (in part because they’re hooked up to different reservation systems), it’s sometimes possible to get a fare on one site that appears sold out on another.

I recently needed to book two Delta tickets for a couple of colleagues. I could get one at a cheap price on Orbitz but not two. So I booked one on Orbitz and the other on Expedia which still had available inventory when Orbitz told me the fare was no longer available.

Of course, your mileage may vary, and that’s why you need to check around.