Differences between arteries and veins. arteries are larger, more muscular and more elastic than veins; they carry blood that is under pressure from having been pumped out of the heart; veins are under much less pressure, so they are not as strong.rtery Structure. arteries have three layers: a smooth inner layer; a strong, muscular layer; and a thin outer layer; connective fibers in artery walls allow for the elasticity needed for the artery to function; arteries are usually larger than veins.