Electronic controller is definitely better. You can set the gate pressure (or whatever other brands call it) to wait until a certain psi is reached before allowing any signal to wastegate, which is what the ball and spring totally guesses . This is what you want for maximum spooling. You can set them up to run different boost curves, different per gear etc.
Also take the place of a boost gauge.
and yes, they are fail safe, so if they stuff up you will be back on gate pressure.