Mining is both safer and more profitable.
Only if the USD per MH/s rate is as insanely high as currently.
I guess with such a tool you can also calculate a USD per MH/s rate under which it would be more profitable to buy, right?
Mining difficulty might be correlated with price - BUT there are and have been serious shifts in there as well!
I really should create a few graphs on my own... I just don't find more convenient MtGox data (idela would be daily weighted averages or even block/2016 block weighted averages!) so I'd have to mess with huge tables in Excel just to prove a point that currently noone seems to realize anyways.