Why not? Its an awesome idea.
Firstly, Manali and Kasol, inspite of being in the same district (Kullu), are very different travel destinations.
Manali, being more reachable and known, is crowded with tourists. The majority are Indian tourists coming for their honeymoons, family vacations etc. Manali has good hotels, better connectivity and is immensely commercialized. As it is so famous and well developed place, it is totally safe to travel and spend time there. People in himachal are in general the nicest people I know, add to that the good security the place has from police as a prime tourist location. It makes nothing for you to worry for safety.
Kasol, whereas, is located off Bhuntar, which comes 50 km before Manali, in a different valley called the. Kasol is located roughly 30 km up above the valley. It is not so well known travel destination. The road is not the best ones from bhuntar to Kasol. Only, backpackers and travelers who want to stay with scant infrastructure, travel to Kasol. Kasol is more famous with foreign travelers, especially with the Israeli’s. They come and spend months in kasol and places ahead which are much more difficult to reach, like Tosh, Barsheni etc. It has very basic accommodations available, no fancy spots. But the whole place has a hippie and retro kind of feel. Laid back Coffee Shacks, places with very different cuisine, lots of israeli influence, awesome quality and cheap art and crafts, you’ll find everything very different here from Manali. Old Kasol and new Kasol aren’t very separate, they are just across a tributary of parvati valley (50 mtrs apart), its basically the same place. In Old kasol, locals has been living from ages, new kasol has been developed due to the tourist influx it has been experiencing. The place isn’t very big, whole kasol spans within 1 km radius. Though, there is very less police present, the locals are much more awesome people. Friendly and always welcoming you. Hence also very safe to go.
Finally, I would say both places have evolved with different influences from different set of tourists who visit there. Tourists who want travel with leisure and don’t bother exploring much, will opt for Manali. Tourists who love to stay as close as possible to the nature and dont care much about the luxury and facilities love to go to kasol. The beauty you get to see in kasol can just hypnotize you. One has to decide what he/she expects from the travel.
Manali is also a nice place with good whether, but crowded. You would like it if you have that kind of taste.
Hope it answers the question. Go and travel any place you like to, you’ll not regret doing it.
For me, its kasol, where I want to go again and again.
Leaving with an awesome click from Kasol by a friend.