Unless you race or are rich.....
The 3DL's are unnecessary. Nothing against North's 3DL, they are some of the best sails out there for performance. Sure they look good, hold there shape well, but you do have to handle them with more care than a standard dacron sail and they are a significant upcharge compared to a high quality dacron sail. They are prone to delamination and mold/mildew. If you are going to use the headsail on a RF, expect an even shorter lifespan compared to a hank on. The J105 that I sometimes crew on has 3DL headsails and they rip and delaminate frequently. Granted they are a few years old, but it seems that every 3 to 5 weeks, some repair has to be done on them.
If you can afford them and afford to replace them in 2 to 5 years, go for it. If you're like me, I can't afford dropping many thousands every few years, so I go with a high quality dacron sail. For a headsail a high-quality, crosscut dacron sail will be a good substitute. It will hold it's shape well (but not as good as 3DL), not delaminate, and less prone to mildew.
Once the 3DL's begin to delaminate or when a certain percentage of their fibers break, they are basically useless sails, where as a dacron sail, will still "work".
If you liked my advice/response, give me some rep points. If you didn't......well what do you expect, it was free.