IT looks like Tape drives can store more and since there is nothing really mechanical going inside like a head and a spinning disk I would go with a tape drive.
This really depends on your retention period and volume of data to be retained.
We don't use tapes at all anymore as they are to slow for our environment.
As an example, we maintain 30 data points onsite (daily's) and 12 offsite (weekly) providing us with 3 months worth of retention. This is easy enough to achieve using disk based storage.
However, at a previous business where we had to retain data for 7 years for legal reasons, everything would be put on to tape and archived off very as it was never going to be required unless the people in black helicopters came along asking for it.
It really depends on the volume of the data that needs to be stored. Tape drive is an obvious choice if the volume of the data to be stored is very high.