The verdict is that Shimla is mainly a more crowded destination but all its attractions are quite close to the city center. On the other hand, Manali is mainly more for adventure seekers and best visited during winter season. So, if you’re someone who enjoys adventure sports, Manali is a good choice.
Manali is similar to any snow clad hill station, more common for trekking and honeymoon. Leh is worth the price, even if it costs you more, more so, if you are driving to Nubra Valley or Pangong lake.