Buying or mining are both profitable and yes you have a point if I will choice between this two I also prefer to choice buying bitcoin than mining because in mining you need a good equipment that cost a lot plus the electricity you can cost while if you buy bitcoin you can trade this in some trading site or invest in some project that will give you a good profit but this is my own opinion it’s up to you which one will you choice.
Therefore the preferable way is to buy the coins at the time of dump and then sell them at high prices earning huge profits without any input effort.