I agree with Knitette, you do get a better deal in the long run if you cut your own (providing you can do so accurately!). One thing you may wish to consider is an accuquilt or other cutting system if you find you have trouble with precision cutting. It takes guesswork out of it and allows decent cuts. But it is pricey.
If you find you want to experiment, maybe do a blend of both. Buy yardage for the quilts you have material you LOVE and wouldn't mind having scraps of, and buy precut for the rest? Although you will most likely end up with scraps there, too. They multiply you know!
Either way, there is no wrong answer here. Do what is best for you, which may only be found out by trying both
good luck and welcome to the madness!