13 Things You Didn’t Know About Online Travel Sites

1. They know who’s a Mac and who’s a PC—and who's going to spend more.

Last year, Orbitz tracked people’s online activities to test out a little experiment: Do Mac users spend more on travel than PC users? Turns out that on average, Mac users lay out $20 to $30 more per night on hotels and go for more stars, according to the Wall Street Journal. As a result, the online travel site shows these users different, more expensive travel options first. To avoid inadvertently paying more, sort results by price.

2. Their software doesn’t always hook up to the hotel’s system.

A guaranteed reservation is almost impossible to come by—but the risk of finding out your flight or hotel is overbooked increases with third-party providers. The middleman’s software isn’t immune to system errors, so always call the hotel or airline to make sure your booking was processed.

3. Don't be fooled by packages: Often, they're low-end items grouped together.

Ever notice how travel sites recommend one-stop shopping, like a hotel, rental car, and tour package all in one click? These deals usually feature travel that no one wants, like flights with multiple layovers. Check the fine print.

4. If you're trying to save on travel agent fees, you might be spending more with online DIY.

According to the American Society of Travel Agents (ASTA), the average service fee for booking airline tickets in 2009 was around $20. Yet that can outweigh $100 or more in straight savings, as well as added benefits (like upgrades and better flights) you can get from a travel agent. The New York Times’ frugal traveler did a series of test runs, finding the best available flights online and comparing that to what a travel agent could do. The results: usually, the travel agent came in cheaper—fees included.

5. Last-minute travel isn't the same deal it used to be.

At the advent of the online travel site boom, last minute was the time to book—cheap flights! Cheap hotels! Getaway this weekend! But the buy-and-fly magic has ceased to exist; now your sweet spot is about six weeks (or 42 days) before departure.

6. You aren't likely to build airline or hotel loyalty.

Don’t book online if you want to rack up those miles or points—at most, you’ll get the minimum, and your booking won’t make you eligible for any special offers, like double points on weekend stays. Work directly with a company or travel agent to build up the loyalty points that will get you upgrades and priority rewards.

7. Travel agents often can share exclusive perks.

Online booking sites are all about dates, rates, and space, meaning their goal is to put heads in beds, says Misty Ewing at Virtuoso luxury travel network. But for the same price, an agent might have connections and special access. “For example, when traveling in Italy, you can take a cooking class with a local resident in her home—a level of authenticity not provided by the Internet,” she says.

8. Corporate travel needs are probably better done in person.

Planning a small business trip can become a logistical mess, and online travel sites offer little help. But specialty business travel agencies can help their clients with corporate events, meetings, and special services that online travel sites don’t deal with—and might be more likely to get you refunds on unused tickets.

9. Online, you might not see every option.

No travel site will show you options from every airline—and no one includes budget-friendly picks like Southwest or Ryanair. But travel sites leave out even more options for lodging, listing big names and omitting comfy little inns, bed-and-breakfasts, and rentals from places like HomeAway.

10. Once your trip is purchased, you're on your own.

All trips, no matter how well planned, are vulnerable to cancelled flights, subpar hotel rooms, or torrential weather. An online travel agency can’t provide assistance the same way an agent can. Basically, when you arrive at the airport or hotel, you’re just another client who booked at the lowest rate. “You can’t VIP yourself,” says Ewing.

11. Online deal sites can't give first-hand experience.

A website can’t tell you the exact location of the room, the view, the size, or whether or not the room needs renovation. You'll have to do more research on your own or risk getting stuck in the dimly lit room in the back of the building with a picture-perfect view of the A/C shaft.

12. They also aren't as current as an agent...

An online travel site often isn't going to share if construction is happening in the hotel or somewhere near by. Researching on other sites might turn up this information, but an agent is likely to be the best resource for knowing what's going on.

13. …or know who else will be staying there.

Planning a romantic getaway for two? That won’t matter to a group of high schoolers on their senior trip at the same hotel. An online travel agent can’t tell you when a large group is in-house, making it uncomfortable for the few guests who aren’t in the group.