Chopta is called as mini Switzerland of Uttarakhand. Filled with velvet meadows, views of Himalayas, evergreen forest, Chopta trek is a medium grade trek which is done for 5 days. The distance between Chopta and Rishikesh is 5 hours.
On the other hand Kedarkantha trek is a 6 day trek which is a summit and mainly undertaken by beginner and seasoned trekkers. Stunning views, beautiful villages, and the feel you are in the Himalayas is guaranteed. From Kedarkantha Rishikesh is 5 hours away.
My advise would be Chopta for its stunning beauty, and nature. Someday you should try Kedarkantha trek too.
Will share a few tripoto links written by travellers pertaining to their travel to Chopta trek see if it is suitable for your travel.
https://www.tripoto.com/uttarakhand/trips/chopta-trek-on-5c72770688a52
2N&3D Chopta Trek
https://www.tripoto.com/trip/chopta-trek-5fb8f2dfbc358
Kedarkantha trek tripoto links
https://www.tripoto.com/india/trips/kedarkantha-trek-uttarakhandhttps://www.tripoto.com/uttarakhand/trips/kedarkantha-trek
Kedarkanth comes is easy to moderate treks which takes 3 days while Chopta is an easy trek of 1 day. It depends on your priority both the treks are beautiful in its own way.