According to me,MS Chauhan is a better choice. This book provides a good conceptual pack of questions that will help you clear your concepts and also provides anomalous questions that may be asked in AIIMS exam. Himanshu Pandey has a lot of answer key mistakes and some of its questions are very confusing that can take up a lot of your time.
As MS CHAUHAN has a lot of questions i will recommend you to mark the questions that you think are good and should be revised again so that while revising your organic chemistry u won’t need to do that whole bunch of questions again just do the marked ones.
All the best!