If you are asking is Sikkim better spot to visit, or Meghalaya is better spot to visit? If I have not understood the question properly, kindly do clarify once again. Sikkim is one such lovely spot filled with meadows, snow capped hills and Himalayas side. Meghalaya called as abode of clouds has mesmerising nature surroundings. One of the highest rainfall spot in India. Since rains are lashing in both the places, it’s safer to travel after monsoon season that is after September.
I should suggest you to visit Arunachal which will gives you similar himalayans beauty and combine the tour with meghalaya. you can enjoy both the beauty of himalayas with Clouds of meghalaya.