Good morning Nicolasmm18,
Welcome to the Apple Support Communities!
I understand you purchased a iPhone XS two days ago, and you believe the Lock screen is not as responsive as other iPhones you've tried. I would suggest updating your iPhone to the most recent iOS (which is currently iOS 12.1.4).
Update your iPhone, iPad, or iPod touch
Try adjusting the Auto-Lock setting on your device. (Settings > Display & Brightness > Auto-Lock). You can adjust this setting from 30 seconds to Never. I think 3 Minutes is a good starting point. Then restart your iPhone.
If you purchased the iPhone at an Apple Retail Store or online at Apple, you can return the device within 14 days in the United States if you are unhappy with your purchase for any reason.
Apple Retail Store Purchase Policies
Take care.