If you hold bitcoins for around five years, the original price might double or triple or even be ten times the original, on the other hand if you hold dollars for 5 years the price won't increase enough to make you a profit like bitcoin does.
We can touch dollar but bitcoin not. Thats one of the different but in this case we will not talk about that.
We are more concern about the vaue of something. Bitcoin can grow double in short day although it has a weakness being drop because its volatile. This is the most case why people stay in bitcoin. We want to try our luckiness.