Asking what camera will get you better nighttime pictures of the castle is like asking which oven will bake you a great cake. As others here have said, it's not just the camera, but learning effective techniques that can make the greatest difference. That's not to say that some cameras aren't better than others; with cameras you generally get what you pay for. However, even a $35,000 camera will get you blurry images.
To get good low light pictures, you should stabilize the camera. Usually that means using a tripod, but I understand that you don't want to get bogged down with bulky camera gear. So, here are some alternatives to using a full-sized tripod. You can stabilize yourself by leaning against a pole, wall, or something sturdy, and hold the camera close to your body and as steady as you can (and hold your breath). However, that's probobably the least effective technique. You can stabilize the camera even more by placing it on top of a trash can (they're all over the place at WDW) or on top of a table, etc. This works in a pinch, but it really limits the angles at which you're able to shoot. You can improve things by using a mini-tripod (sometimes called a tabletop tripod). Mini-tripods fold down to just a couple of inches for easy storage (it can fit in your pocket or purse!). You can place a mini-tripod on a table or trash can or you can use velcro to attach it (tightly) to a pole or railing. I'm not mentioning the gorillapod or flexpods, because they're a little bigger and thicker than other mini-tripods, and I get the feeling that you'd prefer something tiny. Some people use a beanbag instead of a mini-tripod. Finally, use the camera's timer (you know, the timer that lets you include yourself in a picture). The timer allows a few seconds for the vibrations caused by you pressing the button to subside before the picture is taken.
Finally, because you mentioned comparing the pictures on these boards to your own photos, I'd like to point out that the pictures on these boards are not full-sized; they've been shrunken to fit in the posts. Images can appear sharper when they're sized smaller. So, don't beat yourself up: it's not really fair to compare your full-size images to the shrunken (and sometimes artificially sharpened) ones you see here.