Kodaikanal and Munnar are two very important tourist places in our country and a good number of tourists visit these hill stations every year, especially during the summer and autumn times. Both of them are popular destinations and people go there to enjoy their holidays and have fun and entertainment in the lap of great natural beauty. I have personal experience of visiting both places and from my observations, the main differences between these two places are as below.
Approach
Both the places are accessible by road but it takes quite a good time (about 6-7 hours road journey) to reach Munnar from the nearest main city that is Kochi in Kerala. On the other hand, it takes only a few hours to reach Kodaikanal in Tamilnadu from the various towns, cities, and railway stations near it (Madurai, Batlagundu, Palani, Oddanchatram, Kodai Road, Dindigul, etc).
Natural Beauty
Coming to the natural beauty aspect both places are full of natural beauty, scenic landscapes, waterfalls, and other such natural attractions. Still, if we see a large-scale landscape then Munnar offers a very open and extensive view while Kodaikanal offers limited views within the steep hills and valleys. However, while travelling around Kodaikanal some open landscapes are also seen at places.
Fun Activities
On the fun and environmental side though both the places offer a lot of fun activities and entertainment Kodaikanal has got an edge over this point and the tourist will find a more rustic and ethnic touch in the Munnar area as compared to Kodaikanal.
Accommodation
There are a good number of Hotel accommodations in both places and the visitors can book their accommodation in advance to avoid disappointment at the last hour. Budget hotels are also available in both places at reasonable rates and tourists who are on a limited budget can manage their stay in these hotels or guest houses comfortably.
Food
Plenty of food options are available in both places and one can have food of one's choice. Nowadays small eateries are available in most of the hill stations and the same is true for Munnar and Kodaikanal. I liked the South Indian snacks and food which are served in some eateries and hotels in Munnar.
Local Transport
 On this front also both are comparable but in Kodaikanal one can have more shared taxi or shared auto options as compared to Munnar. So both are very good destinations for tourists but based on my personal experience I would rank Munnar above Kodaikanal.