While highly unlikely (assuming you both have the same setup, tires, etc)
The reason your truck would feel less sensitive rotation wise would be due to the fact he can rotate harder and smoother is due to less nose weight.
People who run a heavier pack especially find that moving the battery back 10mm helps with this greatly, allowing you to run more antisquat and will just keep the rear end more planted all together.
Consider the fact most of you turn qualities comes from the rear tire slip angle (rear toe).
If it's rotating to much add toe in, and vice versa. More toe in also majorly stabilizes your straight line acceleration.
M2C sells a chassis pan that has the 10mm back mod built in if you don't want to modify your battery tray on the stock pan the crude way. (albeit, it works just as good)
Also, generally speaking... The twichiness can be tamed without needing to reduce end points or over all servo speed. What really makes the difference is the speed at which the servo recenters/return rate. On most mid to highend radios you can adjust the return speed for the steering without effecting the rest of the servo's motion.
This allows you to keep your full turn in and initial turn in speed so you aren't limiting your self in the technical sections, but stabilizes things majorly.
As for the twichiness when you land a jump, that can be due to a number of things such as your throttle control and the angle at which you touch down IE nose high or low...
However there is an adjustment that helps correct this assuming everything else is setup to your liking. That adjustment is called "bump steer"
Bump steer is simplified to the understanding of how it effects your toe-in/toe-out when the suspension is compressed.
To further understand this you can hold your chassis up light on the tires and then slowly compress your truck down with your hand til it bottoms out and watch closely how the toe changes degrees from full droop to compressed. If it doesn't change then you have 0 bump steer. You can add some in so that it gives you more/less toe as it compresses from level to tune the way it will react upon touch down off a jump.
Bumpsteer is one of the little discussed topics in chassis tuning, but that's the easy run down.
If you're running a technical track you might want to play with your ackerman setting as well. If you are a power on through a turn sorta driver then you will like more ackerman. If you like quicker initial turn in and more off power steering through the center of a turn, then you will like less ackerman.
Lots to digest, but I highly recommend playing with these features to get a feel for what they do before you get serious about chasing a setup sheet. No matter how good that sheet will work for "ProX" if it doesn't meet your driving style it will not help you without knowing how to tune it to your liking of feel.