According to the American Express Spending and Saving Tracker, 15% of travelers plan on using frequent-flier miles to push down the price of their summer vacation. Some will be getting a lot more out of those rewards than others, as SmarterTravel analyst Tim Winship notes that vacationers who are frequent consumers and not-so-frequent fliers get a lot more mileage out of credit cards that dole out travel rewards from their issuer's program rather than an airline-specific card. The big difference is that airline capacity controls affect airline rewards programs, meaning that someone who's racked up a free flight with an airline will likely have to fly off-peak or whenever the airline deems it convenient. With cards such as the Capital One Venture ( COF), Chase ( JPM) Sapphire and Citi ( C) Thank You Premiere, the card issuer buys the ticket on the cardholder's behalf once enough miles are cashed in. Those rewards pile up much more quickly, too, with American Express' Blue Sky card giving cardholders a $100 annual allowance for baggage fees and a $100 credit toward travel (airlines, hotels, car rentals, cruise lines, travel agencies, tour operators, online travel agencies) for every 7,500 points they accrue, at a rate of roughly 1.33 cents per point. Though a free flight is preferable, a little help with fees never hurts. "These bag fees are waived if you're an elite-status flier, and there's programs like United's where if you pay $250 a year you can fly with as many bags as you want all year with you and your family," FareCompare's Seaney says. "If you use a Delta or Continental Visa ( V) card, they waive the fees for bags. And American Express platinum card members get reimbursed $200 toward bag fees."