I was in B for both and thinking about it, there was more gear runners themed out tanks with sparkle skirts, as @LAKid53 mentioned I get the colors now. Thou the ones decked out in Princess hair, glitter and dress I congratulate them on being able to run that distance in costume.Might depend on the corral aswell. I often start in the front and see (a lot) more running gear than costumes. Some are slightly themed, but a lot of race shirts or own gear aswell.
It's up to what you like most, and it's a blessing that you can do either without it being silly
I admire those in full costume and wigs too, it's fun seeing all the costumes and the creative lengths people go. Lots of Sparkle everywhere!For Princess Half weekend, you're underdressed if you not dressed as a Princess or in the colours of one (think Disney bounding). The former Star Wars weekend the same (I will miss the running group dressed as TIE fighters).
I go with the colours, rather than an actual costume. I've got lots of Sparkle skirts that I can pair with a running top to be Aurora, Snow White, Cinderella, Belle, Leia, etc. I admire those runners in full costume, like the guy that always dresses - in full costume, including wigs - for Princess weekend.