What is your intended use for this pistol?
Target/competition, or defense?
Some would say that a 3.5lb trigger is too light for a gun that is to be used for defense. That being the case, they would recommend a heavier spring to bring the pull to the 4.5-5lb range. (Just an average, some say a little lighter, some heavier)
That being said, the answer is up to you.
A new firing pin may work for you, a lighter one will definitely have a bit more speed for a given spring strength. But speed is not the only factor in the amount of force applied to the primer by the striker.
Momentum= Mass*Velocity
Kinetic Energy= 0.5*Mass*Velocity^2
Kinetic Energy is probably the most important, but momentum is important too.
So the question is... what changes will give you the most increase in momentum and energy?
A lighter pin may enable speeds that are fast enough to compensate for the lack of mass... but a stronger spring will increase speed of the existing striker much more reliably.
Basically, the lighter striker is lowering one variable in hopes that the gains in the second variable will cause a net increase in the final figure. It is possible that a lighter mass will only gain enough velocity to equal out the loss of mass.