lol. look like you're excited.
bet you can't wait till next year huh?
Depends if you want to reuse the jacket for another cosplay. Actually, they all have the pros. I'll list some and I'll let you decide
For the star. people always give more recognition for things that the cosplayers had made themselves so the star it would make it unique. but it's permanent? so no reusablity (or this doesn't apply)
The cornet would work as a bag and a prop. So more people would want pictures of it, also it's a excellent icebreaker. Konata and her cornets. possibly most expensive
Pins are less noticeable, less expensive. And easy to remove in case you want to reused the jacket
Now pardon me while I'm fangirling over a Konata cosplaying as a vocaloid.<3