I own all three and like each one !
The park finish is more traditional MilSpec finish that looks great when new and also looks great worn, in my opinion. The park finish will show holster wear in time however will wear somewhat better than the Blued finish.
The Blued finish is beatiful when new, looks okay worn but wears quickly due to holster carry and handling. I like a nice blued finish but, in my opinion, mars easily.
Stainless, is a great looking finish, rust "resistant" and wears well. Should this finish mar, scratch or wear, it can be buffed out, back to the original looking finish with little effort. In my opinion, stainless is, by far, the beast finish (material) for a pistol, especially if you use it, holster it or shoot often.
Other here may have different views, but this is my 2 cents !!
Dog