I run smaller. No real reason until I had my custom made. On it, I can run any cog between 12 and 24 teeth without messing with chain links. A 42 up front gives me the option of true mountain gearing; 42/24 = 47 gear inches and 42-12 gives 95". (At least this was true mountain gearing for my first 2/3s of a century. One century being one hundred years, not miles )

Ben