Scyther and Pinsir yield the highest points, followed by Scyther and Butterfree.
The higher the level, the more points you get.

What we suspect...

The less damage the Pokemon took when you caught it, the more points you get.

Sadly, sometimes if you do these to get the most points possible, a random venonat or something still beats you. There appears to be a random factor involved. Just keep trying. You can use the time change code to try as many times as you want any day of the week so testing it shouldn't be a problem.