The Benq 1620 have my vote, because of better burn quality. Mine require high quality media, and in return I get exellent burns.
High quality media don't cost much theese day, that's why I only buy quality stuff.
Generelly the LiteON DVD burners I have owned, had problems with mid or low quality media.
If you only will buy low quality media, you better consider a NEC 3500.