> I can have several ideas in mind, and have a concrete implementation made for each, making it easier to compare alternatives.

I would ask what exactly are you comparing. I don't think I've ever wrote 2 versions of code to compare between each.

I've written exploratory code. A few lines to quickly inspect the behavior of module/function because it's undocumented. If something needs tuning, I surface the parameter in the interface, hook it to an harness to plot and manually tune.

I've also written alternative implementation of some feature, that later was abandoned.

But I've never written multiple versions of the same feature at the same time. I either model it (algorithm) or sketch it (interfaces or some other flow). It's way easier to interate with those than some demo/prototype code. The latter is when we settled on a solution and wants to fine tune it.