Bathroom sizes. Which should be bigger?

[Bill Kramer]

Design question:

Converting a 3 bedroom 1 bath ranch to add a 2nd bathroom in a bedroom to create a master bedroom. But im torn on a design question:

Should the master bedroom bathroom be larger or smaller than the public bathroom?

I will be dividing up a decent size bathroom to do this. Personally i feel the public bath should be smaller. So what seems to give tye most appeal?

This is an STR, but may eventually be a LTR if airbnb doesn't play out well.