As dumb as this may sound, you need to look at "quality" of turnovers too. Some turnovers aren't the QBs fault (ball bounces off receiver or wrong route run). Other times the turnover is exclusively the QBs fault (wrong read, missed throw, staring down receivers). Other times it is a nature of the play call (50/50 ball, home run shot).Thompson 24 TD passes with 9 Interceptions
Martinez 14 TD passes 10 Interceptions
Fumble turnovers is another stat to look at too
Martinez had a lot of turnovers that were a result of missed throws or trying to make something out of nothing. Instead of throwing the ball away and living for another day, he'd extend plays too long and would fumble or throw a pick (he also sometimes had good things happen). He was better about this decision making last season than in years prior, but still had a number of mistakes in this area.
I haven't watched enough of Thompson to know what his turnovers looked like.