I had different phases in life.
Before I got my first job, I was all cash. I could tell you exactly how much money I had in cash at any time. I still saved, but my savings rate was low.
After I got my first job, I was using cash and credit card. One day I was looking at my expenses, and cash was a big part of it, and I tried to figure out what I was spending it on. And I realized it was all on junk. My savings rate was high (>50%), but had room for improvement.
More recently, I have mostly stopped holding onto cash. Once I stopped, my CC bill didn't change, just my cash withdrawals stopped. So for me, moving away from cash helped. And my savings rate increased.
Later, I realized because of all the years I only had cash, and during that time I wasn't paying any bills, I had associated it with fun money. But now, instead of a finite amount like I had as a child, it was infinite, I could always go to the bank and get more. So when I wanted something I didn't need, I subconsciously asked myself if I had the cash for it. Now, I don't have cash for it, so I don't get it.
So for me, credit cards are the way to go, and it would take more work for me to make cash to work like it did before I had a job. Does this make me weak willed? Maybe, but I don't need the willpower the way I do it.