The only fittings where you will notice a serious difference is those fittings that scale against a person, and that where there is a figure involved. Using 1:72 instead of 1:60, the parts will just look a little "dainty". Figures would probably just pass off as humans of smaller stature. Overdo it, and, of course, the boat will look like it has been hijacked by a visiting school trip party. If you try to go the other way, whatever you fix the fittings to will look overcrowded and heavy, figures would look like a race of giants.
Just dont go finding 1:60 bits and mix them in.........