Hi, So one destination is on the east and the other is to the south. Meghalaya is a place which can be visited in all the seasons with its vast greenery and waterfalls and more amazing places unlike Kerala which would be pretty hot in the summer clicking 50°C. so it's upto you to choose the destination after reading the above detail. Kerala is definitely a beautiful destination with many activities and sight seeing places. nevertheless Meghalaya has some serene places. if u have more time in ur hand visit Kerala or else visit Meghalaya.
The answer depends on the kind of experiences you want to have.
It is common knowledge that the Northeast has some of the best and untouched spots in India. Meghalaya is a great destination with astounding hills and lush greenery. You can head on to the other sister states from here too. Kerala, on the other hand, consists of hills stations, beach towns and forests. If you want a variety in the places you visit, you can opt for Kerala. Besides, a trip to Kerala would be slightly cheaper than an excursion to Meghalaya from Delhi. It would also take less time to explore more.
Another factor to consider is that Meghalaya being a state amidst hills can be visited during summer as well. November is when the dry season begins in Kerala and is one of the best times to visit the state. Attaching a few guides that you can consult before coming to a final decision. Have a great trip!