Some people like to flash their credit cards, especially if it is one of those fancy platinum ones associated with higher-income earners. Before platinum cards it was gold cards, but they have lost their lustre, with diamond the new platinum. Is titanium next?

But when it comes to the spending habits of most people, the cards' associated loyalty schemes are rarely worthwhile.

Usually, a lot of money has to be racked up on them and, if card holders do not pay off the whole debt within the interest-free period, the rates are almost double that of ordinary cards.

A decade ago, the discounts were mainly on airline travel. Now, there are rewards including shopping vouchers and petrol, and one card even has a dining program for those who eat out a lot.

Financial comparison site Mozo released a study in August that found average spenders struggled to come out ahead after accounting for the cards' annual fees. These fees have risen to about $150 a year on rewards cards from about $125 in 2010, although the fee can be more than $400 a year and a few do not have any annual fees.

Over the same time, the fees on ordinary cards have come down from about $60 to $45.

With some exceptions, Mozo found that at least $20,000 has to be spent on a loyalty card each year to just starting getting some value from the rewards program.

However, the average spend on all credit cards is estimated to be about $16,000 a year.

Rewards cards are not for Mr and Mrs Average, the managing director of Mozo, Rohan Gamble, says.

''For the average consumer the rewards cards do not make sense, in our view,'' he says. ''Unless you are a high spender, just forget the rewards cards.''

The sting in the tail with rewards cards comes if the cardholder does not pay off the balance owing, in full, within the interest period.

Rewards cards charge interest of the order of 20 per cent a year compared with about 13 per cent for ordinary cards.

These credit card interest rates are mostly unchanged despite the Reserve Bank cutting the cash rate by 1.5 percentage points during the past year.

Most cards - not just rewards cards - charge interest on the full balance, even if the cardholder pays the required minimum balance within the interest-free period.

If the minimum repayment is not made on time, interest can be charged going back to the purchase date and the interest-free period cancelled on subsequent purchases.

Often, it is cheaper to pay with cash, especially if the company providing the product or service charges a fee for paying with plastic. Credit card fees are not only charged by retailers but also by airlines, taxis and hotels.

Taxis can add surcharges of up to 10 per cent of the fare for those paying with a credit card.

Rewards cards were better value when they first appeared more than a decade ago.

The Reserve Bank found earlier this year that shoppers needed to spend more than $18,000 on a card to earn a $100 shopping voucher in 2011, whereas $12,400 was needed for a $100 voucher in 2003.

A decade ago, they were fairly simple and card holders were able to more easily work out if they were getting value. And it was before discount airlines became big players. Consumers who are not frequent flyers are unlikely to get much value from cards with flight rewards. They are going to be better rewarded by shopping around for the lowest air fares.

The card providers say it is competition that is driving the increasing complexity of the loyalty schemes, but it also suits the providers that the cards are harder to compare.

Still, for those who do spend up big on their cards and always pay off their card debt, in full, within the interest-free period, they can be worthwhile.

Factors to consider in a rewards card include the number of points earned for each dollar spent and whether there is cap or limit to the number of points that can be earned.

Another important factor is the time period, if any, before the points expire, and whether or not the card has ''cash back'', where unused points can be redeemed for cash.

For Mr and Mrs Average, a low-cost credit card that can be used for overseas travel, for purchases online and in emergencies, may a better way to go.

Or how about avoiding credit card debt altogether with a debit card linked to a transactions account.

A couple of debit cards have rewards programs.

It is early days, but Mitchell Watson, a senior financial analyst at researcher Canstar, expects more debit cards to start adding rewards programs to them.