I don't think it is a matter of style. It looks better to match the finish of the door knob to the rest of the room, and so a split-finish knob set makes sense. I've done it in a couple of bathrooms. You don't notice the split, but you would notice the orb in a nickel bath.

Never heard of doing that. Can you buy hardware like that? Or do you buy two sets and throw half away?

I'm thinking of doing that in my MBR. The lighting in the BR and fixtures in the bath are ORB, so I want to change the door HW from builder brass to ORB, but keep the knob on the hallway side the brass to match other doors. What I plan on doing (since all the doors except the BR door to the hall and the linen closet door are pockets) is to buy a privacy set in ORB and only change the BR side (with the little push-button) and the bathroom side of the closet (doesn't bother me that knob will have tiny hole) and leave the inside of the closet brass.

Another thing you can do (might be cheaper) is to just buy "dummy" knobs, though you can't get those in privacy, only closet type. Then just leave the working parts in place, pop off the knob and trim ring and replace them with the dummy trim.

I ordered mine as a split finish set so I didn't have to buy two (although I've also done that). Try DoorKnob Discount Center. They carry the major brands. I found their customer service to be very helpful.

Here is a link that might be useful: DoorKnob Discount Center

I was going to do something similar since our baths have chrome fixtures but I was replacing all the door hardware in the house with ORB. I decided against it.

For one thing, and this may be a big difference, I have walnut stained trim and doors so my ORB hardware does not stand out much where the chrome does. And for another, the doors are mostly opened so the ORB hardware is what you see most of the time anyway.