K2,Captaris Vs WF

Can somebody let me know what are the outof box activities which differentiates K2 & captaris from WF.

It is very much necessary for me as WF is not going to cost anything while other workflow management softwares cost very much.

I know that Wf is a framework while others are products but is there some specific domains or activities while are very difficut to make and are present in other workflow products.

Thanks everybody

Cheers