Honestly, I don't know. I don't use Nero anymore.
The latest tests I did with Nero 6.6.0.8 were not conclusive at all. The 32K gaps were lost, and burning a DL DVD with Nero can be a real hassle.
If you really wants to use another application, use RecordNow (either Stomp or Sonic version.) It should respect the 32K gaps, and be able to burn DL DVDs. But it's not free.
Also, note that Lightning UK! will release a new burning application (without the DVDD 'illegal' stuff) called
ImgBurn. PgcEdit already supports it in v0.6.1 final. ImgBurn should be released soon, and I will release the new version of PgcEdit immediately after.