The no-brainers are: If you need more than two seats, then you need a Prius. If you like small, and fun, then you need an Insight. If you want a stick, then you need an Insight.
The most important thing you need to do is drive both. As far as the driving, the Prius is fun because of the all electric mode, but it isn't nearly as fun because it is a bigger car and less nimble for that reason and you can't get a manual.
I personally do not like the Prius cockpit at all and hate the way it gives you (or doesn't give you) the feedback on the hybrid system. Others love that part. Don't make your decision without sitting in both cars and driving.
If you are comparing automatic transmission models, then both will get similar mpg and both are low emissions.
The most important thing you need to do is drive both. As far as the driving, the Prius is fun because of the all electric mode, but it isn't nearly as fun because it is a bigger car and less nimble for that reason and you can't get a manual.
I personally do not like the Prius cockpit at all and hate the way it gives you (or doesn't give you) the feedback on the hybrid system. Others love that part. Don't make your decision without sitting in both cars and driving.
If you are comparing automatic transmission models, then both will get similar mpg and both are low emissions.