The variations in the models of Sig pistols apply to just about every model they have. For example, the "Equinox". For all of the P22x pistols (and maybe the 232, don't quote me on that) they have this, which is the equinox grips (thicker than standard), "highlighted" parts of the slide where theres no finish, it's just meant to look good and shiny. You also get a fiber optic front sight.
Then there's the "tactical" versions, which are very similar to the standard, but come with extended magazines, front slide serrations, and a threaded barrel.
Then there's the versions with the beavertails on them, the name escapes me at the moment. Nothing terribly special there.
I don't think that having different versions of a given model is such a bad thing. You have your choice of caliber, version, and trigger setup (DAK, standard DA, and SAO for some, think X5 P226). There's a gun to fit anyone's needs or wants. And now with the E2 option for grips, you can get even closer to finding the perfect fit. The main reason that stores don't always carry every single setup is the demand for it. But it's a good bet they can get one ordered for you. Sigs are expensive, and having a bunch as overhead wouldn't be a smart idea unless you were a larger business that could move them for sure. If you don't like what you see when the order comes in... don't buy it!
Options are always good to have.