I use tags for the very simple reason that it's simplest and easiest to then find what I'm looking for. Each project I'm working on has its own tag, so I can easily find everything related to it. But then, I can also tag things "receipt", "joey", "tax-deductible", etc. when needed. You can't stick a note in two notebooks (unless you're okay with having multiple copies of notes floating around). It's easy to set up, easy to sort, and easy to find. It doesn't take an intense explanation of how it works, like the notebook approach tends to.
"I used to advocate liberal use of tags but have been cured of that. They're a burden and whatever benefit they provide is by far outweighed by the amount of time they waste." I can't disagree with this enough. You have to be smart about tags, of course - just like you have to be smart about not overdividing content into notebooks. When I started out using Evernote years ago, I tried the notebook approach, as it's what my brain was used to. But, I CONSTANTLY hit walls of, "Wait, does this go in my project support, or in my Receipts notebook? Or in my Tax Documents notebook? Well, shoot! Where do I stick it??" When you use tags, you can tag it with all of these things and can get to it however you're thinking about finding it at the time. I find that sometimes when I'm looking for stuff in Evernote, it's not always due to the same factors. So while one day I might look for it a certain way, the next day I might think about it differently and do a different search. If you don't tag it with all possibilities, you run the risk of losing it to the data monster.
In the end, it's about being able to find what you're looking for, and knowing you can find it. If that means sticking it in one place, where you can only find it one way, then I'm glad that works for you. But my brain's too scattered for that, and I like being able to pull up my notes in a variety of combinations that you just cannot do with the notebook approach (notes tagged "receipts" and "work", if I want to pull up all work expenses; "giftidea" and "dad" and "funny" if I want to get my dad a gag gift, etc.). I've got over 3,500 notes sorted this way and I've never been unable to quickly find what I'm looking for.