Of the two, I generally prefer neon colors. I do still like pastels though, and get especially interested in pastels during the Spring in the lead-up to Easter.
despite my profile having more bright and vibrant colors i actually prefer pastels / more muted colors.. the difference between my twitter account and my TBT account is a little crazy lol
I have a slight lean to pastel colors because of the cutesy and softer vibe, BUT I still really like the vibe of neon colors. Especially at night if it's all colorful.
My preference will vary depending on my mood. When I'm content, then pastel colors look extra cute that day. However, I can only handle so much of it. For example, my Instagram feed is loaded with lots of pastel colors and kawaii stuff just from looking at Sailor Moon or Animal Crossing stuff. It's fine at first, but then it slowly starts to give me a bit of anxiety so I'll have to move on to the search page.
Between the two, I'd pick pastels. I can only look at neon colors for so long before they start hurting my eyes. Neon used sparingly can look really cool though!