Bitcoins can be called disadvantages.
Constantly increasing the size blockchain.
Very long transfers between wallets.
It is necessary to wait 6 evidence, and it is long!
Many believe that the end will come soon Bitcoins.
How exactly you want to add more data to blockchain without increasing its size? Transfer times are not that long, bigger threat is double spending. You dont need to wait for 6 confirmations you are fine after just 1.
Many people before said that bitcoin won't survive. They all were wrong.