The most obvious difference between cryptocurrencies and tulips is that tulips existed centuries before their rise. These coins are based on an effectively new technology. If you want to compare it to a bubble, compare it to the dotcom boom. How the tulip argument continues to be peddled on HN escapes me.
A big difference is that anyone could grow Tulips; Bitcoin has a supply limit
Tulip mania lasted 9 months. Bitcoin is 9 years old.
Tulips were sold before the mania, just like Bitcoins were.