What is better Nerf stampede or Nerf vulcan?

It's no argument that the Stampede is much more mobile than the heavy Vulcan, and the shield may be slightly useful, but keep in mind that the Vulcan provides about an additional 2 seconds or so in firepower at a time, and it is an Excellent defensive weapon.

Basically, Vulcan if you're going for defense, Stampede if you're going for offense. In my opnion, both are Excellent weapons and provide great support on the battlefield. It's all about your position.