Both Sikkim and Meghalaya are beautiful. You can visit any place in northeast in winter, everything there is mesmerizing. But if i have to choose between Meghalaya or Sikkim, i would go with Meghalaya.
Hello, Both the places would be good, but Meghalaya looks more beautiful in monsoon, when the waterfalls have enough water flow and the valleys are covered in all shades of green. I would suggest that you take a trip to Sikkim in December :) If you go higher up to Lachung & Lachen, you'd get snow there as well. :)
If you want to capture the picturesque view of Himalayan Range, then December is the best season to visit Sikkim. During this time you can be part of various festivals like the Maniram Bhanjyang Tourism Festival where you can enjoy local homestays among many other things. You can also be a part of the Cherry Tea Festival as well as Red Panda Winter Festival. These festivals showcase a different side of Sikkim.