I also like the separate harness but the resin ones so stand out nicely if, as you say, they can be highlighted with paint techniques. I found the PE Sutton Harness provide by Eduard (used on my Mk I Spit) to be difficult to work with because of the separate shoulder pieces and don't really want to do that again.
This is my first resin seat purchase, driven by the ICM's omission of the indention on the bottom and by the fact that I have another ICM Spit (an Aussi Mk VIII) in my stash. Since the seats were sold in pairs, I went for it.