Hi Mariam.

You could select either. It's pointless which is better. siRNA may be more free, cheap, controllable, and effective.

Regards.

There are some minor nuances to each method, shRNA vectors are more suitable for proteins with longer half-life because they are continually expressed and thus inhibit de novo protein synthesis continually. However for shRNA vectors, you need to construct them using a kit, grow them in bacteria and then isolate them which can get somewhat expensive. Whereas with siRNAs they are ready-to-go and you can achieve good transfection rate and knockdown, but that depends on many variables.