I have been using SMARTvector 2.0 Lentiviral shRNA, do I need to change to SMARTchoice shRNA?

Not necessarily. SMARTchoice is a platform by which multiple promoter and reporter options exist for SMARTvector 2.0 shRNA constructs. The original SMARTvector 2.0 backbone utilizes human CMV to drive expression of the shRNA; this promoter is very active in many cell lines and cell types, and successful gene silencing is achievable. However, hCMV promoter activity can vary from cell to cell and less-than-optimal promoter activity may impact shRNA functionality. To identify the most active promoter in your cells of interest, we recommend using the SMARTchoice shRNA Promoter Selection Plate, which will allow you to assess seven different promoters in a single experiment.