The road from Manali to Leh is more popular than the route from Sarchu to Leh via Zanskar due to several reasons. The Manali-Leh route offers stunning landscapes, famous high-altitude passes like Rohtang and Tanglang La, and better road connectivity. The Sarchu-Zanskar route involves more challenging terrain, river crossings, and limited facilities, making it less accessible for many travelers.