It's a trial and error process. It's not just physical, it's mental as well. The weight is the weight, like every one else has pretty much said, go in as small as you feel comfortable so you can (hopefully) be the bigger competitor
You want to go in with a positive mindset though. For me, I probably go in smaller than I want to and for the weeks leading up, feel miserable. But come competition day, I'll feel very positive in that I know I've done everything I could and left nothing on the table with regards to training and S&C (since I have to do way more conditioning to help get the weight down). I've had competitions where I've felt happier given that I didn't have to lose as much weight but when it came time to compete I was thinking I didn't do enough work because I didn't have to be as disciplined. "Maybe I shouldn't have gone out with my friends and had that burger" type of thing.
To each their own