Hello,

You can pursue MPC even if you have pursued MEC earlier and you can enter commerce colleges even after having a B.tech degree so MPC has diverse options which opens up commerce career option as well whereas MEC has narrow career options and you cannot pursue engineering courses with MEC.

You can apply for direct enrollment by taking admission in 11th class again or you can fill the examination form privately from any school and give MPC exams.

All the best!