Source has 18% bigger models than 1.6, with 36% more hittable surface area and 76% larger heads. Source has up to 40% less recoil (depending on the gun) than 1.6, making the guns easier to control. Source has more powerful flashbangs than 1.6, increasing the number of player deaths while blind. Source has the exact same movement speed as 1.6, which means that proportionally, models move more slowly. Additionally, as proven time and time again, top 1.6 players are able to transition to Source and continue to compete on the highest level of competition, while the opposite is not possible.