Both spot is great you have to pick relies upon your selection of interests.
Recommended course:-
Himachal :-
Alternative I (Best time to visit whenever of the year)
Day 1: Landing in Delhi – Shimla (370 Kms Approx)
Day 2: Shimla – Kufri – Shimla (15 Kms approx)
Day 3: Shimla – Kullu-Manali (250 Kms approx)
Day 4: Manali – Rohtang Pass/Solang Valley – Manali (55 Kms Approx)
Day 5: Manali Nearby Touring
Day 6: Manali – Dharamshala (260 Kms Approx)
Day 7: Dharamshala – Dalhousie (120 Kms Approx)
Day 8: Dalhousie – Khajjiar – Chamba – Dalhousie
Day 9: Dalhousie – Amritsar (250 Kms Approx)
Day 10: Amritsar – Chandigarh
Day 11: Chandigarh-Delhi
Alternative II (Inborn Himachal/Spiti Valley Trek, Best time to visit June to October)
Day1: Pickup from Chandigarh and drive to Shimla (125 km)
Day 2: Shimla to Sarahan (170 km/7 hrs)
Day 3: Sarahan to Sangla (92 km/4 hrs)
Day 4: Sangla to Kalpa (51 km/3 hrs)
Day 5: Kalpa to Tabo (145 km/6 hrs)
Day 6: Tabo to Kaza (70 km/entire day with Dhankar and Lalung Visit)
Day 7: Kaza-Kibber-Kaza
Day 8: Kaza – Kunzum La – Chandratal Lake
Day 9: Chandertal – Rohtang Pass – Manali
Day 10: Manali to Chandigarh (Approx.300 KM/8-9 Hours)
Day 11: Chandigarh-Home
Uttaranchal:-
Choice I (Best time to visit whenever of the month)
Day 1 : Delhi – Rishikesh
Day 2: Rishikesh – Mussoorie
Day 3 : Mussoorie – Auli
Day 4 : Auli
Day 5 : Auli
Day 6 : Auli – Kausani
Day 7 : Kausani – Binsar
Day 8 : Binsar – Munsiyari
Day 9 : Munsiyari – Patal Bhuvaneshwar
Day 10 : Patal Bhubaneswar – Mukteshwar
Day 11 : Mukteshwar – Bhimtal
Day 12 : Bhimtal – Sattal
Day 13 : Sattal – Nainital
Day 14 : Nainital – Corbett
Day 15 : Corbett-Delhi
Choice II (Chardham Yatra, Best time to visit May to october)
Day 1: Haridwar-Mussoorie-Barkot (220 kms, 06 hrs drive):
Day 2: Barkot-Yamunotri return:
Day 3: Barkot-Uttarkashi (115 kms, 5 Hrs drive):
Day 4: Uttarkashi-Gangotri-Uttarkashi ( 100 kms each side, 3 1/2 Hrs):
Day 5: Uttarkashi-Guptkashi/Sitapur (210 kms/8 hrs).
Day 6: Guptkashi – Gaurikund-Kedarnath (40 kms , 1/2 hrs).
Day 7: Kedarnath – Guptkashi/Sitapur:( 35 kms)
Day 8: Guptkashi/Sitapur – Badrinath (220 kms/8 hrs):
Day 9: Badrinath – Joshimath/Rudraprayag (45/165 kms):
Day 10:Joshimath/Rudraprayag-Rishikesh-Haridwar (220/140 kms, 08/05 hrs)