DDL's are safer and more consistent in speed.
Torrents tend to be much, much faster, but yeah Torrents can die a lot easier than a DDL with age. But hell I do find some 5+ year old torrents that still push 1mb/s, which is great.
If you have the right ISP, then there's no danger to using them either.
Torrents are also easier to find most of the time, IMO. They're also more convenient for big files that would otherwise need to be split into multiple DLs.