The two options are good ways to earn bitcoin.  The only differnce is mining needs focus, time, uninterrupted power supply, suitable and high technology computer and proper understanding how to do perform mining.  If you have those qualities and requirements then, mining is good for you.  On the other hand, if you don't have even one of those requirements but you have money to use for, then, investing is good for your.   Mining and investing plays a great part in bitcoin.  If you can perform the two at the same time, then, you do not have to choose.