Check your viability numbers. Beersmith looks to be giving you the starter volume based on 96% viability. Mr Malty is going off 71%.
In mr malty, there is a viability calculator when you input the date. Wyeast uses a packaged date if memory serves. Input that date into the calculator and it will make the viability calculation and suggest your starter size from there
If you use a white labs yeast, they give a "best by" date, which is, and someone here correct me if I am wrong, 4 months after the package date. So if you use white labs, subtract 4 months from the date on the vial and use that in the calculator