Engagement is a special time in a relationship. The commitment is there, but it's a new stage, and life is becoming busy with wedding planning. An engagement shoot is a great time to slow down and carve out a block of time to focus on each other. It's fun, it's low pressure, and it can incorporate your favorite things or place which often don't work into the wedding day.
Some location ideas are the iconic DC monuments, under the cherry blossoms, garden, farm, Old Town Alexandria, city, country, vineyard, where the proposal took place... the options are endlenss and if you need ideas, I have plenty more!
It's also casual, unlike much more formal wedding day pictures (limited by wedding clothing, if nothing else. I doubt you'll sit on the ground in your wedding gown). And there's no time pressure, no one is waiting for your return.
So it's all very different and valuable and can't really be compared to the wedding day. And the other benefit is, you get to know your photographer and become comfortable in front of the camera, which takes a lot of pressure off the wedding day. And your photographer gets to know the two of you and how you relate as a couple. It's a win-win!
One of my favorite uses of engagement pictures - beyond simply having great pictures of the two of you which many couple need - is making a guest book. This is the perfect way to enjoy your pictures and your guests notes all in one easy to store place. Couples and guests love them!