It depends on the mood of your traveling.
If you are willing to go for better sightseeing , better food and stay , market place and facilities , you can go for Manali .
If you want your trip to be peaceful , relaxing and want try stuff you can visit kasol .
Chitkul I haven't visited yet .
In my opinion , if you are planning for kasol then rather staying there you should visit Tosh for better view .