Just like with all things- it’s all a matter of personal preference. These materials are very different and serve very different functions, so it should be really easy to determine what type of fabric will worth for you. Microfiber isn’t exactly the softest and comfortable material, but it excels in being incredibly compact to be able to fit multiple into a tote bag, and it is really able to soak of the water better than cotton materials. Additionally, it dries really fast in the hot sun more so than cotton. The benefits of cotton are that it feels really nice and soft when you wrap it around you after an afternoon in the ocean or in the pool, and it feels just as soft as you lay on it on the sand. The downside is that it doesn’t dry as fast as microfiber, and it takes up a lot of room in your tote bag.