The Sig 1 is the most barebones stripped out Greubel ever which says a lot since GF is a more is more kind of brand. It was produced in relatively fewer numbers compared to many GF models including the contemporain. My conspiracy theory is that because Didier left GF they didn't want to keep re-releasing the Sig 1 in new colorways like they usually do, at least not with his name on the dial, and it spoiled the concept for future Signature X watches. Anyway, irrespective of production numbers, the simplicity of the watch is itself a meaningful part of the GF evolution. GF went to the top of the mountain with quad tourbs and complications before coming back to the basics likely inspired by the Naissance D'Une Montre project. The S1 was the first GF with an in-house balance assembly (wheel and spring), the first and only with Geneva stripes, and the only with a traditional / slow 18k bph.
The contemporain is closer to the Greubel ethos of more - more barrels, more levels in the architecture, more engraved text, faster beat rate, power reserve, boxed sapphire, it is more watch in a smaller package. It is really an evolution of the S1 in some ways, an upgraded and better iteration, the ultimate and now final of the classic GF balancier watches until they introduce something new. I imagine this is the more livable of the two, the longer power reserve makes for a watch that doesn't need to be wound everyday the boxed sapphire probably saves the bezel from a lot of wear, and the smaller size makes it that much easier to wear. Potentially the dual barrels and higher beat rate make for a more accurate watch and visually I like the effect of the mirror polished backdrop to the balance wheel.
Despite all practical advantages of the contemporain, I prefer the S1, there's just less stuff and it creates more negative space and virtual depth despite being the thinner watch. I think with Greubel there is an ever increasing mountain of technical accomplishment and complexity (and cost) but the S1 is a bookmark as the least of the GF watches and to me more interesting because of it's deviation from more traditional GF codes. Like the Porsche 914 or a Dino, I like that it's uniquely less than what cam before and after.
