^^I can't recall size-wise, but I like the Oval because it's more like an actual old key. I've never seen a heart key IRL. And the oval size was more substantial.
Don't get me wrong, I love hearts. I even have a heart tatto for a special reason and pick heart shapes over almost any other...just in this case, I myself went for the "real" old key look.
I think you have to decide which one speaks to you, you know?
Side note: I was in TJMaxx browsing the jewelry because it's inexpensive and sometimes they have cute stuff, great prices. I saw my crown key. It was smaller - but otherwise identical. Kinda bummed me out a little.