Sean,
I would look at the cost/availability comparison of the two, throw in a little preference(which wood do you like better?) and go with the winner. I would take into consideration that oak may not show its blemishes and/or damages as well as mohagany and can also offer you the option for lighter tones. But the bottom line is any hardwood floor is as good as the quality of the installation and the quality of care post installation. Beauty and light traffic=mahogany Beauty and high traffic=oak