We are planning on going with the Franke Little Butler. But I haven't actually seen them next to each other yet. I'm curious what other respond with.

Very happy for you that you are going with the OTF :). I love mine and really, really wish I had two of them. Have no idea of what to recommend with it, just love the KKF. Three cheers for the one true faucet! Looking forward to what you select:)

Here is my instant hot/filtered cold setup. On the ther side I have a soap dispenser. I added his after the fact in a tweaking of my kitchen (now I am planning a total redo moving the kitchen). I had the hole added to the granite later so I echoed be placement of the existing soap dispenser. It works well as you can get a cup of tea or filtered water while someone else uses the main faucet. The faucet is a Moen Arbor Motionsense which I love (other than than at the handle has come loose a bit they sent a free replacement kit of some sort which I need to fix so far just had my husband tighten it but it worked loose again). I will move both faucets to my new kitchen. I think I will put the hot/filtered at the prep sink in the new as the location makes more sense for tea/water although I also like to use the hot in some cleanup uses

“We may not do the air switch to keep it from looking cluttered.” The little air switch button will not make anything look cluttered. You do not say how many holes your faucet has. A single-hole single-handle faucet is less cluttered than one with 2 seaparate handles requiring 3 holes in total. Regarding placement of the air switch, regardless of which side you have it, it needs to be installed closer to the corner of the sink, rather than close to the faucet, see pic below. That is because you don’t want dripping hands from the faucet to be dripping onto the air switch constantly.