Depends

Dressing is when you're dressing for yourself and dressing up is simple when dressing up to show off

Dressing is just for any day where you can go anywhere wearing something "normal", but dressing up is when you put more effort in your outfit and it looks more dressy/fancy. Dressing up is more rare.

"Dressing" is a step above "getting dressed." To me, dressing involves putting some thought into a cohesive outfit the night before to make sure I look well put-together. After dressing, I'll put at least a little effort into hair, makeup, and jewelry.

I 'get dressed' on days when I don't plan to leave my house, and that's really just about covering myself.

I rarely have the opportunity to dress up, but it involves bold choices. Floor-length dresses, short dresses, and false eyelashes. I often try to coordinate, or at least not completely clash, with my partner if we're dressing up.

Dressing is utilitarian, dressing up is decorative and to an extent more consciously performative

Ok, Dressing is to cover your Body with garments so you are not naked.
Dressing up means to me selecting garments and putting them together for a Special occation.

there's none.

I hate, loathe and despise dressing up

yes

Dressing up is ocations like party, wedding and stuff, just dressing is a daily routine.

Dressing is what you do every day. Dressing up is special somehow. It’s up a step from the usual, whether up into the halloween spectrum or into elegance.

I chose the outfit vs. someone else chose the outfit.

I believe dressing up is much higher then the normal dressing.

Dressing up implies that one is going somewhere somewhat more formal. So I have "formal" jeans & "informal jeans". lol I do put on something a bit more refined when 'dressing up', but still maintain that ol' Hippie in me. I'm not here to impress anyone. I go out to enjoy myself.

I can dress for everyday and then for special occasions I can put on a dress and hoping that I look good in it.