I would recommend the higher compression with 9.5 to 1 but with Mod S cams. I built several early engines (one 2.7 with RS pistons and Mod S cams) and dynoed all of them in the same car. You can see the results in the thread below. Mod S cams were better than E cams everywhere.
https://forums.pelicanparts.com/porsche-911-technical-forum/1151593-dyno-summary-testing-early-2-4l-2-5l.html
john