Dell vs Lenovo trackpoint/nipple/trackstick mouse drivers?
You can play with setting different values to different trackpoint properties and maybe compare props of your Lenovo trackpoint with Dell's.
Use the command xinput list to see all input devices and their IDs. Then use xinput list-props $ID to see what the device is capable of and xinput set-prop $ID $PropID $value. I wrote some examples in another topic, but it's about Thinkpad trackpoint: here. There's also a brief instruction how to make changes permanent.
I think your issue is related to acceleration or movement smoothing.