I had used both mechanical and non mechanical.
Both also same brand, APEXI.
Non-mechanical (electronic)-
Like :
1. the jarum will move when u start the engine (like DEFI)
2. can record the highest/lowest boost
3. NO hose behind the meter, just a small wire going to the controller
Dont like :
1. the sensor usually place inside the engine - easily to spoil due to heat
2. more expensive (have to buy controller some more)
Mechanical
Like :
1. sensor in the meter itself, so can last long (no heat)
2. cheaper and more choices
Dont like:
1. hose coming out from behind the meter, depend on the location u place the meter, sometime can be disturbing.
2. cannot record, no moving jarum when start etc