Making a new dark UI theme - help me decide an element colour

I've pretty much completed my new clean dark theme for the GIMP 3 series, but I'd like some feedback on one thing before I release it.

Should I use a light or dark tone for the separators? If you compare the two images you'll see what I'm referring to.

I think the lighter separators are easier to see and the darker ones are less distracting.

Which do you think is better?

I know I have a bias towards making things low-contrast and 'smooth', sometimes overly so, and I'd appreciate some outside perspective.

Also posted to Mastodon if the images here are struggling to load on your Lemmy app, like they do sometimes on mine: https://mastodon.social/@jpicture/116255975518406081