Well I did try to restore an ex-NTbackup DLT tape using Veritas BE10 and it sort of read it OK but I could not find a way to catalog the tape from BE10's 10,000 pulldown menus and options. What a total load of c**p this program is, done to justify the £1000+ (corporate version) price tag. I suppose if you need to backup live databases then you need a special tool for the job...
Re the other tape formats: I have no experience of the others you mention. An old friend, who goes back to the earliest days of Unix, has always spoken well of DLT and its superb backward compatibility. He can read tapes done 20 years ago. So I went for DLT. The drive wasn't that expensive either; £500 for a Quantum DLT-V4 which will do 80/160GB. The £28 Sony tapes which I use will do up to 320GB. Currently I am recording 120GB of data, most of which is not significantly compressible.
There are other tapes which are much faster but they haven't been around for long, so I would avoid them unless I needed something special. Remember that to feed 80MB/sec to the tape drive, you will need a drive array. No single HD is that fast, sustained.
I've been using DAT/DDS since about 1996 and while it's been pretty good, it's been far from 100% reliable. I lose perhaps 1 tape in every 10, due to weird errors. And these are HP or Sony tapes, nothing cheap. Once it records OK then it tends to be OK though.
The DDS drives don't last too long either; 2-3 years after doing a full tape once a week so perhaps 100 backups, which is not good for a £400 tape drive. The faults range from inability to correctly sense tape capacity (DDS1/2/3/4) to require permanent cleaning. The repair cost is so high it's never worth repairing.
It's really weird that after all these years, tape still rules. I recently thought that blue-ray DVD writers will take out a chunk of the low-capacity (DDS4) tape market and they might, but DVD reliability is the pits - no way one could rely on that medium for say 10 years. One tiny scratch...