Hi Sirish
Go with the second one, don't miss out an opportunity of kheerganga trek, one of the most finest treks you will ever see, especially it's hot water bath as well.
This is going to be tight schedule believe me either do delhi dhramshala bir biling mcleodganj tuind trek 11-14 march last year and that too when i stayed in bir only for one day so 6d \5n is good for it or else do kasol tosh manikaran kheerganaga trek and manali , solang and vashisht