I think buying is a safer, simpler and lazier option, which can also bring some long-term profit and easily make $40k into $100k over a couple of years. As for mining, it means not only initial investment which you that need to cover by profits (when you buy Bitcoin, you can always pull your money out, and you'll get more out of it than out of selling mining equipment, probably). You also need to cover the electricity bills, which can be huge. Not to mention maintenance, so that your equipment doesn't break. And, possibly, taxes for doing business, maybe some permits to do that etc. So I'd go with buying Bitcoin.