Actually I agree with him. The touchpads on the xps and MacBook are similar in optimal conditions, but the XPS one seems way more sensitive to sweat/oils from the hand and then stops working until it is cleaned. I have hyperhydrosis so my hands sweat alot, never caused an issue on my MacBook, but the XPS doesn't handle it as well.

On the software side, the MacBook can also handle finger movements quickly followed by a tap much better, while on the XPS if you do really quick movements followed by a tap the cursor will jump back a little. (Annoyingly enough to accidentally hit the close tab button when trying to switch tabs). I reported this to dell and they said the issue lies in the MS driver.