For a different perspective...
Buying the fixed sight model gives you a lot more options down the road. The slide is machined a good bit to fit the adjustable sight unit, and retro-fitting will be much more limited than if you have the simple one-cut dovetail of the fixed sight model to deal with.
MMC offers this adjustable sight that will fit into the
fixed sight Kimber slide. I had them (MMC) custom mount a set of their sights into a Makarov I own. I thought they might look "blocky", but after I received the slide back from them I was pleased. The sights are nicely rounded and of a robust design - after over a year of being thrown into the glove box of my car & tossed into my home "easy access" locations, they haven't budged. The are offered in black, 3-dot, & a bunch of night sight options along with different finishes.
Obviously, buying the adjustables fitted from the factory is going to cost less than adding them later - simple economics. The slide is machined once instead of twice, you own 1 sight instead of 2, the labor to install 1 set is less than the labor to install, remove, then install, etc. If you are certain you want adjustables & you like the Kimber unit, I would buy it equipped that way.