The Glock 19 was preferred over the Sig because of its consistent trigger pull which translates to better accuracy. Much of it is because of the polymer design. The Sig uses all-metallic. Polymer is also a lighter sidearm option compared to the all-metal construction of the P226. Polymer also has better corrosion resistance. Given that Navy SEALs usually do aquatic operations resistance to corrosion especially in saltwater is important. Hence, the Glock 19 was preferred over the P226 mainly because of its polymer construction design. There was never a problem with the P226. It’s still a great handgun. However, the Glock 19 is better suited for what the SEALs need.