Do your own figuring on the actual costs of using both. I've often heard very skewed figures about how expensive disposable diapers would be. But that's usually figuring you're buying the most expensive brand-name disposables and changing your baby 10X a day. Most babies do fine with inexpensive store-brand disposables, and because they're more absorbant they need to be changed less often than cloth ones. You'll also want to weigh your extra garbage costs against your extra water/detergent/electricity/washer wear costs.
You may also want to consider using disposables at least for the first month, when you're still recovering from delivery, dealing with post-partum changes, adjusting to life with your new miracle, and probably dealing with sleep deprivation. Plus the baby's poop is really loose & easily leaks at that age. Who needs extra laundry chores at a time like that? You may not feel like saving any planet, and happily pluck an endangered Snowy Owl for its feathers to use if you've run out of wipes.
Of course, if you get used to the convenience of using disposables, you may not want to make the switch to using cloth afterwards. I too planned on using cloth diapers until my firstborn had to be delivered via c-section. My pals convinced me to use disposables at least until I healed from the surgery. But by then it was like hearing "well now that you've recovered from your operation you can go back to cooking over an open fire in the back yard". I figured I could do other things to save money & help the environment while cutting down on my diaper/laundry chores.
Still, there are all sorts of groovy new products available to today's Mommies, snug stylish wraps that fit even the tiniest of tushies, thin absorbant washable liners, not like those thick droopy cloth diapers of old. You may not be able to use them for washing your car after baby's done with them, but they may make cloth diapering much easier to do.
Congratulations on your bundle of joy!