I think it all depends on your pattern and how it's drawn. If I know I'm going to be 'fitting' parts from a pattern, I'll usually cut two or, three small parts (or, pieces of parts) to see how they fit and then I can tell if I need to cut inside, outside or right on the lines. If the parts to be assembled are fairly straight (rather than curved) it's pretty easy to cut a little large and then sand down to needed size on a disc or belt sander.
Dennis