It seems probably in Gurbanee the word "VASATu" is for Naamu wherever used and the word "BASATu" for wordly materials.
Although both words are synonym in their meanings.
There is one more meaning connected to the word BASAT as Dwellin whereas the word VASATu is exclusive reference for specific thing in context of its application.
Reference:: Sikh Philosophy Network http://www.sikhphilosophy.net/sukhmani-sahib/37864-sukhmani-sahib-astpadi-5-sabad-1-a.html
Reference:: Sikh Philosophy Network http://www.sikhphilosophy.net/showthread.php?t=37864
Prakash.s.Baggal