Polka dots for a more fun, playful, energetic mood. Stripes are more formal in my opinion.

For me personally, small polka dots placed in lines make me itchy, and I have a weird, strong dislike of stripes. I like large polka dots randomly placed best. :)

polka dots are to dalmatians what stripes are to zebras.

polka dots are more whimsical

stripes are more deliberate

polka dots are like paint drops, random and no order, where stripes must be made purposely.

Depends on what you want to use them for.