Of course women don't only breastfeed because of ease or saving money by not buying formula. There's a whole lot of health benefit of breast milk that formula comes close to immitating but not fully.
That said - you're question was really about which is easier. Breastfeeding is easier but it is a commitment. Your body adjusts to the needs of your baby providing a different type of milk to newborns than 6 month olds. The quantity grows as your baby grows to provide a lot more for a one year old than an infant. Once your baby is insync with your baby it is very hard to skip a meal or 2 (leave baby with babysitter with formula) - Those meals will be building up in your brests - very uncomfortable.
If you are going to commit to breast feeding you will need a good pump to pump bottles when you are away from your baby. The Medella in Style pump is http://amzn.to/12lOBJz is excellent since it has great suction and does twobreasts at once so you finish in less than 10 minutes
Breastfeeding is easier and also wonderful - but it's a commitment so it's worthwhile to buy the right tools to make it work for you