My vote goes to On Every Street, of all the DS albums this is by some way the one I play the least - it is the one I am most unlikely to listen to as a full album, and the one with the fewest tracks I'd go out of my to play individually. While the album has some great moments (I love the title track, especially the outro riff), as a whole I find it their most uneven work. Also, there are tracks that feel like inferior versions of the hits from Brothers In Arms, which lack the qualities that made the original songs so widely appealing, the two most obvious examples being The Bug (revisiting Walk Of Life) and Heavy Fuel (revisiting Money For Nothing). In the former case, although Walk Of Life is not one of my favourite DS tracks, I remember hearing it on the radio at work one time and noticing that other people started humming along to it. It has a 'catchy radio pop song' quality which reaches people who otherwise might not be into DS, which I don't think The Bug succeeds at. Likewise, nothing in Heavy Fuel can match the immediately attention-grabbing Money For Nothing riff which appeals to less blues-oriented guitar fans.
I agree that OES doesn't quite fit with the other DS albums, but is also quite different from MK's solo albums with the possible exception of Sailing To Philadelphia. I also sometimes wonder if a track like How Long (which I do like) might have fitted better on Golden Heart, I like the song but it feels really odd as the final DS track. The title track from Brothers In Arms feels like a more natural conclusion to their studio discography.