Krabi is a better place, the hotels in Krabi will be very spacious and have a good scenic view. All I would say is enjoy your time in Krabi. Thailand is actually a beautiful place to visit surrounded by many beaches
Hi Ritu! both Phi Phi and Krabi islands are beautiful places. Which is better is a very subjective matter, depending upon your likes and dislikes. Here are a few trips that may give you additional information which might help you decide. Happy Travelling!