Width and tread depth are the same.
The only difference is that the 19" tire is more flexible, and so will maintain contact better.
2014 BMW ///M5 Individual Frozen Grey, Silverstone Full Merino, Piano Black, Exec Pkg, Drivers assistance plus, LED Pkg, Bang and Olufsen, 20" 343M Forged Alloy Wheels
Upgrades: Eisenmann Sport with M Performance Carbon tips, Dinan anti-roll bars, Bel StiR+, ALP
2015 Jaguar F-Type R Coupe
2015 Mercedes-Benz C300 Sport