Both are in option. Best is you can travel to Himalayas as you get option but it's a bit far. So for the short trip you can travel Uttrakhand i.e weekend.
Both have their own perks.. Cannot be compared. It depends upon you what type of place you want to go. For me i personally like Himachal as there are more greener treks and greener mountains. And Uttarakhand is bit rough type land more rocky an muddy and dry. So you first decide what you like and plan accordingly. But if you ask about my choice i would suggest Himachal.