Personally I love my stacking washer and dryer and I'd rather do laundry in the hall than a bathroom. However as you said you'd be left with a random closet in the bathroom. You could use it for guest towels but closet off the kitchen is more useful.

If you end up putting it in the hall, why wouldn’t you combine that space into in the bath into the closet of the bedroom? Maybe I misunderstood that it’s already built.

I had a hall laundry in a condo once. It was fine. But, your hall closet doesn’t look big enough to keep laundry soap, clothes basket etc. —where will you store all that? If did it in the bath you would have some room for those things. That would tip the scales in favor of the bath for me.

Hall. Just couldn’t do laundry in a bathroom.

In the guest bath.

Because:

You can give the bathroom in BR #2 a bit more floor space by reducing the depth of the hall closet by not needing it for laundry appliances and

An open door into the master BR that swings to block access to the laundry closet would drive me bonkers (You enter the BR w/ a basket of dirty clothes then you have to close the BR door before you can open the door to the laundry area... and repeat when you need to shuffle loads to the dryer and distribute the clean clothes....) and

The bathroom location puts the laundry a bit further removed from the wood floors.

Either location, I would strongly consider giving the laundry space 'wet room' level waterproofing. Or a floor drain at a minimum.