Well, both answers are invalid because I'm a girl! But uh… I use both, depending on what I'm doing. If it's some sort of service like getting my hair done I'll pay in cash because that way it's easier to slip a few dollar bills in to tip.
There are some huge advantages to using credit cards though, assuming you pay them back before they charge you an interest. Here's some stuff I found, which is probably only applicable in the US:
First, you'll want to get a Blue Cash Preferred card from American Express. The card is ideal for families and people who spend on gas and groceries. You'll get 6% cash back on groceries, up to $6,000 spent annually, as well as an unlimited 3% rewards on gas and department stores. But more than that you can take advantage of the gift card trick to up your rewards rate on virtually any spending to 6% - just buy gift cards to home depot, starbucks, the gap, wherever, at the grocery checkout line. You'll get the full rewards rate anywhere that offers gift cards. Crazy, right?
Now, it does have a $75 annual fee but if you make $1,000 in purchases with the new card in your first 3 months you'll get $100 back. You'll also get a year of Amazon Prime (2 day shipping on any order on Amazon which is amazing) for free if you meet that spending requirement in the same time period.
6% of 6000 is $360 you'd be looking to make back every year, which you can easily achieve just from groceries and gift cards (bought from a grocery store) to wherever you need to buy stuff. In addition to that since you get unlimited 3% on rewards on gas and department stores you're looking to make quite a bit more money back. Assuming you spend ~$350 on gas a month that works out to around 4200 a year which would get you $126 back. So at this point you're getting $411 a year (I subtracted the $75 annual fee already) for doing virtually nothing but micro managing your purchases to use your card. Obviously counting 3% back from department stores you could make even more money back annually, which is pretty nice.
There's some other neat ones too, you can just skim around and see if any of them are better than the ones you have: http://www.nerdwallet.com/blog/top-credit-cards/nerdwallets-best-rewards-credit-cards/
You guys could check around in your own areas too and see if there is anything that does similar and try to take advantage of it. There's a lot of cards for different various rewards. I figure most everyone probably gets gas and groceries but if you travel a lot or something there's cards for that too. Some cards even upgrade you to first class and get you access to the lounge.
