Choosing a microcontroller for a project is a very tough decision. If you look for discussions about this matter you will find hundredths of pages with discussions, debates, argues, all of them with valid arguments claiming microprocessor x is better and yet none of them give enough substance to decide what's better.

I'll be more pragmatic and will start with the parts I have more quantities in my bins:

• PIC16F688

• ATMEGA8

Then I'll check if they meet the requirements for this project:

1. One external IRQ for the signal from distributor (points, hall sensor, etc)
2. One I/O for driving the power transistor
3. Two ADCs, one for the battery voltage and another for the Vaccum signal

Optionally:

• Two ADCs for potentiometer inputs (for tuning charge time and base delay)
• One USART for sending debug messages

Both will do!!

I'll need to get deeper into the project details before I decide.