STO clarification

HI Gurus,

Can anybody please clarify the following for the STO

1) we have a company ABC that has plant in both mexico and US. The US plant is under company code 1200 and the mexican plant is under company code 1100. Now when we need to get inventory from the 1100 company code plant to 1200 company code plant, will it be regualar PO with NB doc type or a STO with UB doc type?

Thanks

Anusha