Should I choose a sleeveless or short-sleeve triathlon jersey?

Short-sleeve jerseys are more aerodynamic at speeds above 35 km/h due to the aero-textured sleeve fabrics covering the upper arms. Sleeveless jerseys provide better cooling and are more comfortable during the swim and run. For sprint and Olympic distance in hot climates, sleeveless may be faster overall due to better thermoregulation. For long-course racing and time trials, short sleeves with aero fabric are typically the faster choice.