Spend money to save money? Just use Mint, it's free (an annoying ad or three when you fire it up)
I think this is poor advice. I vote to use both! I use mint to track spending/transactions/balances but YNAB to actually plan out my spending and saving. If you actually use the software and follow their "4 Rules" it will change the way you think about money.
In my experience, you are both right. Using everything you can get your hands on that works for you is the right way to go. I personally hesitate to spend money on any software that is normally priced at double the average cost of any other commercial software especially when there are many free tools out there. This cost is not actually for life, you do have to pay for upgrades. Never assume just because you pay for it, that it will work for you. Free software, if done right, can be just as good. Its been paid for by other means.
Don't forget, there is always excel, and the handy dandy "export to .csv" tool found on every financial website. I will never ever enter my transactions manually. That has never helped me. I make mistakes.
I was using Mint religiously for about a year before it got sold to Intuit. I admit that without Mint I would not have brought my debt down like I did. I paid off 25K of credit card debt over a year. I have a beautiful screen shot of my mint debt graph going down down down (its here somewhere). I gave up on Mint because with the Intuit transition, we lost the responsiveness of the development team to fix the bugs. They moved toward a community forum for a help desk, where I spent alot of time contributing. It increasingly became clear that bugs were not getting fixed and they added more features that bogged down the program. I haven't logged in for 3 years because I started using another application called Finance Works.
Finance works is also an Intuit product, free and hosted by my credit union. You cannot get this product alone. Finance works has its flaws too, but it has what mint didn't have and that is a rolling count of my income and spending. I have it set up to look 2 1/2 months in advance. So if I have money left over this month I see how it is needed for extra expenses next month. This is really working for me right now. It does not show me a graph of the rate of my debt paydown like mint does, so I cannot focus on that, instead I focus on living within and under my means and saving whereever possible (which goes toward paying down debt).
My final advice to everyone considering buying commercial money software is always take advantage of the trial period. Make sure you use it as much as possible during the trial (dont just use it once then buy it). You have nothing to lose at all! If over the course of this trial you run into something just plain wrong, you didn't buy it!